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• Chaves, Davi A. D.; Filho, J. C. Corsaletti; Abbey, E.A.; Bosworth, D.; Barber, Z.H. & Blamire, M.G. [Show all 10 contributors for this article] (2024). Using quantitative magneto-optical imaging to reveal why the ac susceptibility of superconducting films is history independent. Physical review B (PRB). ISSN 2469-9950. 109(10). doi: 10.1103/PhysRevB.109.104510. Full text in Research Archive
• Chaves, Davi A. D.; Valerio-Cuadros, M.I.; Jiang, L.; Abbey, E.A.; Colauto, Fabiano & Oliveira, A.A.M. [Show all 14 contributors for this article] (2023). Magnetic field induced weak-to-strong-link transformation in patterned superconducting films. Physical review B (PRB). ISSN 2469-9950. 108(21). doi: 10.1103/PhysRevB.108.214502. Full text in Research Archive Show summary

  Ubiquitous in most superconducting materials and a common result of nanofabrication processes, weak links are known for their limiting effects on the transport of electric currents. Still, they are at the root of key features of superconducting technology. By performing quantitative magneto-optical imaging experiments and thermomagnetic model simulations, we correlate the existence of local maxima in the magnetization loops of focused ion beam (FIB)-patterned Nb films to a magnetic field induced weak-to-strong-link transformation increasing their critical current. This phenomenon arises from the nanoscale interaction between quantized magnetic flux lines and FIB-induced modifications of the device microstructure. Under an ac drive field, this leads to a rectified vortex motion along the weak link. The reported tunable effect can be exploited in the development of new superconducting electronic devices, such as flux pumps and valves, to attenuate or amplify the supercurrent through a circuit element and as a strategy to enhance the critical current in weak-link-bearing devices.

• Pinheiro, L.B.L.G.; Jiang, L.; Abbey, E.A.; Chaves, Davi A. D.; Chiquito, A.J. & Johansen, Tom Henning [Show all 12 contributors for this article] (2022). Magnetic flux penetration in nanoscale wedge-shaped superconducting thin films. Physical review B (PRB). ISSN 2469-9950. 106(22). doi: 10.1103/PhysRevB.106.224520. Full text in Research Archive Show summary

  Thickness uniformity is regarded as an important parameter in designing thin film devices. However, some applications based on films with nonuniform thickness have recently emerged, such as gas sensors and optimized materials based on the gradual change of film composition. This work deals with superconducting Pb thin films with a thickness gradient prepared with the aid of a diffuse stencil mask. Atomic force microscopy and energy-dispersive x-ray spectroscopy show variations in the range 90 nm–154 nm. Quantitative magneto-optical images reveal interesting features during both the abrupt and the smooth penetration regimes of magnetic flux, as well as the thickness-dependent critical current density (Jc). In addition, we observe a gradual superconducting transition as the upper critical field is progressively reached for certain thicknesses. Furthermore, the hysteresis observed for triggering flux avalanches when increasing and decreasing magnetic fields is also accounted for by the Jc profile evolution along the thickness gradient. Numerical simulations based on the thermomagnetic model are in fair agreement with the experimental data. These findings demonstrate that wedge-shaped films are a viable approach to investigate, in a continuous fashion, thickness-dependent properties of superconducting materials.

• Tierno, Pietro; Johansen, Tom Henning & Straube, Arthur V. (2021). Thermally active nanoparticle clusters enslaved by engineered domain wall traps. Nature Communications. 12(1), p. 1–11. doi: 10.1038/s41467-021-25931-7. Full text in Research Archive Show summary

  Abstract The stable assembly of fluctuating nanoparticle clusters on a surface represents a technological challenge of widespread interest for both fundamental and applied research. Here we demonstrate a technique to stably confine in two dimensions clusters of interacting nanoparticles via size-tunable, virtual magnetic traps. We use cylindrical Bloch walls arranged to form a triangular lattice of ferromagnetic domains within an epitaxially grown ferrite garnet film. At each domain, the magnetic stray field generates an effective harmonic potential with a field tunable stiffness. The experiments are combined with theory to show that the magnetic confinement is effectively harmonic and pairwise interactions are of dipolar nature, leading to central, strictly repulsive forces. For clusters of magnetic nanoparticles, the stationary collective states arise from the competition between repulsion, confinement and the tendency to fill the central potential well. Using a numerical simulation model as a quantitative map between the experiments and theory we explore the field-induced crystallization process for larger clusters and unveil the existence of three different dynamical regimes. The present method provides a model platform for investigations of the collective phenomena emerging when strongly confined nanoparticle clusters are forced to move in an idealized, harmonic-like potential.

• Colauto, F.; Carmo, D.; Andrade, AMH De; Oliveira, AAM; Ortiz, W. A. & Galperin, Yuri [Show all 7 contributors for this article] (2021). Measurement of critical current flow and connectivity in systems of joined square superconducting plates. Physica. C, Superconductivity. ISSN 0921-4534. 589. doi: 10.1016/j.physc.2021.1353931. Full text in Research Archive Show summary

  A method to measure the electrical connectivity between square superconducting plates joined by weak link interfaces is presented. It is based on observation of lines where the flow of critical current abruptly changes direction due to the presence of weak links, and the confinement created by the shape of the sample. The method is demonstrated using magneto-optical imaging (MOI) of systems consisting of up to 2 x 2 plates joined to form a larger square. The samples used in this study are Nb films with weak links created by focused ion beam machining. Common features are found in the current flow patterns, which allow to measure the electrical connectivity between the plates by observing an angle between pairs of lines indicating where the current abruptly changes flow direction, so-called discontinuity, or d-lines.

• Motta, M.; Burger, L.; Jiang, Lu; Acosta, Acosta González; Jelić, A.L.Z.L. & Colauto, Fabiano [Show all 14 contributors for this article] (2021). Metamorphosis of discontinuity lines and rectification of magnetic flux avalanches in the presence of noncentrosymmetric pinning forces. Physical review B (PRB). ISSN 2469-9950. 103(22), p. 224514-1–224514-13. doi: 10.1103/PhysRevB.103.224514. Full text in Research Archive
• Chaves, D.A.D.; Araújo, Araujo de; Carmo, D.; Colauto, Fabiano; Oliveira, Oliveira de & Andrade, Antonio Marcos Helgueira De [Show all 10 contributors for this article] (2021). Enhancing the effective critical current density in a Nb superconducting thin film by cooling in an inhomogeneous magnetic field. Applied Physics Letters. ISSN 0003-6951. 119(2). doi: 10.1063/5.0058680. Full text in Research Archive Show summary

  Quantitative magneto-optical imaging of a type-II superconductor thin film cooled under zero, homogeneous, and inhomogeneous applied magnetic fields indicates that the latter procedure leads to an enhancement of the screening capacity. Such an observation is corroborated by both B-independent and B-dependent critical state model analyses. Furthermore, repulsive (attractive) vortex–(anti)vortex interactions were found to have a decisive role in the shielding ability, with initial states prepared with vortices resulting in a shorter magnetic flux front penetration depth than those prepared with antivortices. The proposed strategy could be implemented to boost the performance of thin superconducting devices.

• Valerio-Cuadros, Marlon Ivan; Chaves, Davi Araujo Dalbuquerque; Colauto, F; Oliveira, Ana Augusta Mendonça de; Andrade, Antônio Marcos Helgueira de & Johansen, Tom Henning [Show all 8 contributors for this article] (2021). Superconducting properties and electron scattering mechanisms in a Nb film with a single weak-link excavated by focused ion beam. Materials. 14(23). doi: 10.3390/ma14237274. Full text in Research Archive Show summary

  Granularity is one of the main features restricting the maximum current which a superconductor can carry without losses, persisting as an important research topic when applications are concerned. To directly observe its effects on a typical thin superconducting specimen, we have modeled the simplest possible granular system by fabricating a single artificial weak-link in the center of a high-quality Nb film using the focused ion beam technique. Then, its microstructural, magnetic, and electric properties in both normal and superconducting states were studied. AC susceptibility, DC magnetization, and magneto-transport measurements reveal well-known granularity signatures and how they negatively affect superconductivity. Moreover, we also investigate the normal state electron scattering mechanisms in the Boltzmann theory framework. The results clearly demonstrate the effect of the milling technique, giving rise to an additional quadratic-in-temperature contribution to the usual cubic-in-temperature sd band scattering for the Nb film. Finally, by analyzing samples with varying density of incorporated defects, the emergence of the additional contribution is correlated to a decrease in their critical temperature, in agreement with recent theoretical results.

• Stoop, Ralph L.; Straube, Arthur V.; Johansen, Tom Henning & Tierno, Pietro (2020). Collective directional locking of colloidal monolayers on a periodic substrate. Physical Review Letters. ISSN 0031-9007. 124:058002(5), p. 1–6. doi: 10.1103/PhysRevLett.124.058002. Full text in Research Archive
• Pinheiro, L.B.L.G.; Caputo, M.; Cirillo, C.; Attanasio, C.; Johansen, Tom Henning & Ortiz, W. A. [Show all 8 contributors for this article] (2020). Magnetic flux avalanches in Nb/NbN thin films. Fizika Nizkih Temperatur. ISSN 0132-6414. 46(4), p. 441–448. doi: 10.1063/10.0000868. Full text in Research Archive
• Hioki, Tomosato; Tsuboi, Rei; Johansen, Tom Henning; Hashimoto, Yusuke & Saitoh, Eiji (2020). Snell's law for spin waves at a 90° magnetic domain wall. Applied Physics Letters. ISSN 0003-6951. 116(11). doi: 10.1063/1.5141864. Full text in Research Archive
• Qviller, Atle Jorstad; Qureishy, Thomas; Xu, Y; Suo, H; Mozhaev, PB & Hansen, J.B. [Show all 9 contributors for this article] (2020). Scaling Behavior of Quasi-One-Dimensional Vortex Avalanches in Superconducting Films. Scientific Reports. doi: 10.1038/s41598-020-62601-y. Full text in Research Archive Show summary

  Scaling behaviour of dynamically driven vortex avalanches in superconducting YBa2Cu3O7−δ films deposited on tilted crystalline substrates has been observed using quantitative magneto-optical imaging. Two films with different tilt angles are characterized by the probability distributions of avalanche size in terms of the number of moving vortices. It is found in both samples that these distributions follow power-laws over up to three decades, and have exponents ranging between 1.0 and 1.4. The distributions also show clear finite-size scaling, when the system size is defined by the depth of the flux penetration front – a signature of self-organized criticality. A scaling relation between the avalanche size exponent and the fractal dimension, previously derived theoretically from conservation of the number of magnetic vortices in the stationary state and shown in numerical simulations, is here shown to be satisfied also experimentally.

• Colauto, Fabiano; Carmo, D.; Andrade, A; Oliveira, AAM; Ortiz, Wilson Aires & Galperin, Yuri [Show all 7 contributors for this article] (2019). Anisotropic flux penetration in superconducting Nb films with frozen-in in-plane magnetic fields. IEEE Transactions on Applied Superconductivity (TAS). ISSN 1051-8223. 29(5), p. 1–5. doi: 10.1109/TASC.2019.2898092. Full text in Research Archive Show summary

  The magnetic anisotropy of superconducting niobium films of different thickness was investigated using magneto-optical imaging. A wide range of anisotropic behaviors was generated by freezing in different in-plane external magnetic fields with magnitude up to 1.12 kOe. The critical fields for the parallel configuration of the different samples were calculated, taking into account the strong deviation of the superconducting properties at small thicknesses. Above their lower in-plane critical field, the films are in the mixed state containing coplanar vortices. In structurally isotropic Nb films, when applying a perpendicular magnetic field, the frozen-in vortices were seen to guide the perpendicular ones. It is shown that the anisotropy increases with both the film thickness and the magnitude of the in-plane field. The results demonstrate that the field-induced anisotropy is a highly versatile way to manipulate vortex matter in film superconductors.

• Hioki, Tomosato; Hashimoto, Yusuke; Johansen, Tom Henning & Saitoh, Eiji (2019). Time-Resolved Imaging of Magnetoelastic Waves by the Cotton-Mouton Effect. Physical Review Applied. 11(6). doi: 10.1103/PhysRevApplied.11.061007. Full text in Research Archive
• Pinheiro, Lincoln Brum Leite Gusmuo; Motta, Maycon; Colauto, Fabiano; Johansen, Tom Henning; Bellingeri, Emilio & Bernini, Cristina [Show all 8 contributors for this article] (2019). Imaging Flux Avalanches in V 3 Si Superconducting Thin Films. IEEE Transactions on Applied Superconductivity (TAS). ISSN 1051-8223. 29(5), p. 1–4. doi: 10.1109/TASC.2019.2902788. Full text in Research Archive Show summary

  When developing superconducting devices patterned on thin films, one should bear in mind that flux avalanches might occur for some materials at a certain window of applied fields and temperatures. Although the A15 superconductors are well known and used in a variety of purposes, there are no studies about flux avalanches in V 3 Si thin films. In the present work, we report the observation of flux avalanches in films of V 3 Si, grown by pulsed laser deposition on a LaAlO 3 substrate. The range of temperatures and applied magnetic fields at which the avalanches take place is determined using dc-magnetometry. Magneto-Optical Imaging is employed to visualize the occurrence and spatial distribution of such flux avalanches. Images of the flux penetrated into the samples indicate a clear anisotropic distribution, which is ascribed to a thickness gradient. The observation of flux avalanches reported here implies that attention to this feature must be given when films of V 3 Si are envisaged for possible applications.

• Johansen, Tom Henning; Colauto, Fabiano; Andrade, Antonio Marcos Helgueira De; Oliveira, Ana Augusta Mendonca & Ortiz, Wilson Aires (2019). Transparency of planar interfaces in superconductors: A critical-state analysis. IEEE Transactions on Applied Superconductivity (TAS). ISSN 1051-8223. 29(5). doi: 10.1109/TASC.2019.2899209. Full text in Research Archive
• Zuber, Johannes; Wells, Frederick S.; Fedoseev, Sergey A.; Johansen, Tom Henning; Rosenfeld, Anatoly B. & Pan, Alexey (2018). A new approach to the inverse problem for current mapping in thin-film superconductors. Journal of Applied Physics. ISSN 0021-8979. 123(12), p. 123906-1–123906-10. doi: 10.1063/1.5012588. Full text in Research Archive Show summary

  A novel mathematical approach has been developed to complete the inversion of the Biot-Savart law in one- and two-dimensional cases from measurements of the perpendicular component of the magnetic field using the well-developed Magneto-Optical Imaging technique. Our approach, especially in the 2D case, is provided in great detail to allow a straightforward implementation as opposed to those found in the literature. Our new approach also refines our previous results for the 1D case [Johansen et al., Phys. Rev. B 54, 16264 (1996)], and streamlines the method developed by Jooss et al. [Physica C 299, 215 (1998)] deemed as the most accurate if compared to that of Roth et al. [J. Appl. Phys. 65, 361 (1989)]. We also verify and streamline the iterative technique, which was developed following Laviano et al. [Supercond. Sci. Technol. 16, 71 (2002)] to account for in-plane magnetic fields caused by the bending of the applied magnetic field due to the demagnetising effect. After testing on magneto-optical images of a high quality YBa2Cu3O7 superconducting thin film, we show that the procedure employed is effective.

• Baruch-El, E.; Baziljevich, Michail; Johansen, Tom Henning; Albrecht, J; Shaulov, A. & Yeshurun, Y. (2018). Dendritic flux instability in MgB2 films above liquid hydrogen temperature. Superconductors Science and Technology. ISSN 0953-2048. 31(2), p. 1–5. doi: 10.1088/1361-6668/aa9f41. Full text in Research Archive Show summary

  Magnetic flux instability limits potential applications of superconductors such as MgB2 in practical devices. Previous studies in MgB2 films exposed to magnetic fields revealed the occurrence of dendritic flux avalanches at temperatures below T ~ 10 K. In the present work it is shown that films of MgB2 exposed to a fast-ramped magnetic field display a dendritic flux instability at elevated temperatures, up to 23 K. Such instability can therefore cause malfunctioning of practical devices based on MgB2 films even when operating at liquid hydrogen temperature.

• Hashimoto, Yusuke; Johansen, Tom Henning & Saitoh, Eiji (2018). Phase-resolved spin-wave tomography. Applied Physics Letters. ISSN 0003-6951. 112(7), p. 1–4. doi: 10.1063/1.5018091. Full text in Research Archive Show summary

  The propagation dynamics of spin waves are represented by their dispersion relations. Recently, we have developed a method, called spin-wave tomography (SWaT), to obtain a dispersion relation of spin waves in the long wavelength regime, the so-called pure magnetostatic waves. In our previous studies on SWaT, phase information of spin waves is disregarded. In this report, we demonstrate an advanced SWaT analysis, called phase-resolved spin-wave tomography (PSWaT), to realize the direct observation of the amplitude and the phase of spin waves. The PSWaT spectra are obtained by separating the real and the imaginary components of the complex Fourier transform in the SWaT analysis. We demonstrate the PSWaT spectra of spin waves excited by photo-induced demagnetization in a Bi-doped garnet film, reflecting the characteristic features of the complex dynamical susceptibility affected by magnetostatic coupling in the film.

• Zhao, Yue; Chu, Jingyuan; Qureishy, Thomas; Wu, Wei; Zhang, Zhiwei & Mikheenko, Pavlo [Show all 8 contributors for this article] (2018). Structural and superconducting characteristics of YBa2Cu3O7 films grown by fluorine-free metal-organic deposition route. Acta Materialia. ISSN 1359-6454. 144, p. 844–852. doi: 10.1016/j.actamat.2017.11.050. Full text in Research Archive Show summary

  Microstructure and superconducting performance of YBa2Cu3O7 (YBCO) films deposited on LaAlO3 single crystal (LAO) substrates by a fluorine-free metal-organic deposition (FF-MOD) technique, have been studied by means of X-ray reciprocal space mapping (RSM), cross-sectional transmission electron microscopy (TEM) and magneto-optical (MO) imaging. Combining the X-ray diffraction and the TEM cross-sectional analysis, it is revealed that stacking faults, i.e. YBa2Cu4Ox intergrowths, and ab-plane twins are main defects in the FF-MOD YBCO films. Due to the highly epitaxial growth mechanism related to transient liquid phase, the LAO twinned substrate structure is also inherited in the FF-YBCO films. The low-density planar defects containing dislocations parallel to c-axis result in stripy patterns observed in the MO images. For comparison, the low-fluorine (LF) MOD film show a texture mosaic spread in the ab plane and is little influenced by the LAO twinning underneath, implying the severe structural disorder most likely associated with the large amount of small-angle grain boundaries. Moreover, the higher density of stacking faults was also detected by XRD θ−2θ scan in the LF-MOD film. It is suggested that associated partial dislocations formed at the boundary between the stacking faults and YBCO matrix act as strong linear (or dot) pinning centers. These structural characteristics are well in line with the better superconducting performance of the low fluorine-MOD film, in particular under external magnetic field at 77 K. This work offers an in-depth insight into the correlation between the microstructure and superconductivity in the MOD YBCO films.

• Baruch-El, E.; Baziljevich, Michail; Johansen, Tom Henning; Shaulov, A. & Yeshurun, Y. (2018). Thickness dependence of dendritic flux avalanches in YBa2Cu3O7-x films. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 969(1), p. 1–6. doi: 10.1088/1742-6596/969/1/012042. Full text in Research Archive Show summary

  By implementing a unique magneto-optical system with ultrafast magnetic-field ramping-rate capability (up to 3 kT/s), we have been able to routinely generate and image dendritic flux instabilities in YBa2Cu3O7-x films. In the present work we study the effect of the film thickness on the dendritic instability. Dendritic avalanches in 50 - 600 nm thick films were magneto-optically imaged at 7 K, after ramping the magnetic field from zero to 60 mT at different rates. The data reveal a remarkable change in flux morphologies between the thin and the thicker films. While the former (50-250 nm) display well-developed dendritic patterns, the latter (350-600 nm) exhibit few avalanches with favored branch directions parallel to the film's edges. Several possible explanations for this behavior are discussed.

• Qureishy, Thomas; Vestgården, Jørn Inge; Qviller, Atle Jorstad; Fjellvåg, Asbjørn Slagtern; Meckbach, Johannes Maximilian & Torgovkin, Andrii [Show all 11 contributors for this article] (2018). Energy of dendritic avalanches in thin-film superconductors. AIP Advances. 8:085128(8), p. 085128-1–085128-8. doi: 10.1063/1.5045682. Full text in Research Archive Show summary

  A method for calculating stored magnetic energy in a thin superconducting film based on quantitative magneto-optical imaging is developed. Energy and magnetic moment are determined with these calculations for full hysteresis loops in a thin film of the superconductor NbN. Huge losses in energy are observed when dendritic avalanches occur. Magnetic energy, magnetic moment, sheet current and magnetic flux distributions, all extracted from the same calibrated magneto-optical images, are analyzed and discussed. Dissipated energy and the loss in moment when dendritic avalanches occur are related to each other. Calculating these losses for specific spatially-resolved flux avalanches is a great advantage, because of their unpredictable and non-reproducible nature. The relative losses in energy are much higher than the relative losses in moment.

• Carmo, D.; Colauto, Fabiano; Andrade, Adnei Melges H. De; Oliveira, Alessandro AM; Ortiz, Wilson Aires & Galperin, Yuri [Show all 7 contributors for this article] (2018). Active control of thermomagnetic avalanches in superconducting Nb films with tunable anisotropy. Superconductors Science and Technology. ISSN 0953-2048. 31(11), p. 1–7. doi: 10.1088/1361-6668/aadffa. Full text in Research Archive
• Golovchanskiy, Igor A.; Pan, A. V.; Johansen, Tom Henning; George, Jonathan; Rudnev, Igor A. & Rosenfeld, Anatoly [Show all 7 contributors for this article] (2018). Origin of magnetic flux-jumps in Nb films subject to mechanical vibrations and corresponding magnetic perturbations. Physical review B (PRB). ISSN 2469-9950. 97(1). doi: 10.1103/PhysRevB.97.014524. Full text in Research Archive Show summary

  In this paper the origin of flux-jumps in Nb thin films is established during magnetization measurements using a vibrating sample magnetometer (VSM). Magnetization measurements of the flux avalanche activity show its strong dependence on frequency and amplitude of VSM vibration. In particular, under certain conditions the vibrations induce a transition from a stable superconducting critical state to an undercritical state, accompanied by the 20-fold drop in the magnetic moment. These features allow the elucidation of the origin of the flux-jumps. In contrast to the commonly assumed thermomagnetic instabilities to be responsible for the flux-jumps in Nb films, our results provide solid support for an alternative explanation being due to criticality-built instability well represented by a sandpile. Considering properties of the flux-flow during a flux avalanche regime allows us to estimate nonuniformity of a magnetic field in a VSM sample space developed as a result of vibrations.

• Hashimoto, Yusuke; Johansen, Tom Henning & Saitoh, Eiji (2018). 180-phase shift of magnetoelastic waves observed by phase-resolved spin-wave tomography. Applied Physics Letters. ISSN 0003-6951. 112(23). doi: 10.1063/1.5030342. Full text in Research Archive Show summary

  We have investigated optically excited magnetoelastic waves by phase-resolved spin-wave tomography (PSWaT). PSWaT reconstructs the dispersion relation of spin waves together with their phase information by using time-resolved magneto-optical imaging for spin-wave propagation followed by an analysis based on the convolution theorem and a complex Fourier transform. In PSWaT spectra for a Bi-doped garnet film, we found a 180°-phase shift of magnetoelastic waves at around the crossing of the dispersion relations of spin and elastic waves. The result is explained by a coupling between spin waves and elastic waves through the magnetoelastic interaction. We also propose an efficient way for the phase manipulation of magnetoelastic waves by rotating the orientation of magnetization less than 10°.

• Baruch-El, E.; Baziljevich, Michail; Johansen, Tom Henning; Zhou, Xiaoyu; Jia, Xiaoqing & Jin, Biaobing [Show all 8 contributors for this article] (2018). Magnetic flux instability in NbN films exposed to fast field sweep rates. Superconductors Science and Technology. ISSN 0953-2048. 31(10), p. 1–6. doi: 10.1088/1361-6668/aadacb. Full text in Research Archive Show summary

  Magneto-optical imaging of dendritic flux instability is reported for NbN films exposed to magnetic fields ramped at a fast rate (0.1–3.2 kT s−1 ). The results show that as the magnetic ramp rate increases, the temperature and field range of the instability extends significantly. In particular, the lower and upper threshold fields (Hth 1 and H , th 2 respectively) that bound the field range for dendritic instability are affected. The upper field is found to increase linearly with the applied field sweep rate, a behavior which is discussed in terms of a recent theoretical work (Vestgarden et al 2016 Phys. Rev. B 73 174511). The extended instability range should be taken into account in applications in which the superconducting films are exposed to rapid changes in the magnetic field.

• Hashimoto, Yusuke; Bossini, Davide; Johansen, Tom Henning; Saitoh, Eiji; Kirilyuk, Andrei & Rasing, Theo (2018). Frequency and wavenumber selective excitation of spin waves through coherent energy transfer from elastic waves. Physical review B (PRB). ISSN 2469-9950. 97(14). doi: 10.1103/PhysRevB.97.140404. Full text in Research Archive
• Vestgården, Jørn Inge; Johansen, Tom Henning & Galperin, Yuri (2018). Nucleation and propagation of thermomagnetic avalanches in thin-film superconductors (Review Article). Low Temperature Physics. ISSN 1063-777X. doi: 10.1063/1.5037549. Full text in Research Archive Show summary

  Stability of the vortex matter—magnetic flux lines penetrating into the material—in type-II superconductor films is crucially important for their application. If some vortices get detached from pinning centres, the energy dissipated by their motion will facilitate further depinning, and may trigger an electromagnetic breakdown. In this paper, we review recent theoretical and experimental results on development of the above mentioned thermomagnetic instability. Starting from linear stability analysis for the initial critical-state flux distribution we then discuss a numerical procedure allowing to analyze developed flux avalanches. As an example of this approach we consider ultra-fast dendritic flux avalanches in thin superconducting disks. At the initial stage the flux front corresponding to the dendrite's trunk moves with velocity up to 100 km/s. At later stage the almost constant velocity leads to a specific propagation regime similar to ray optics. We discuss this regime observed in superconducting films coated by normal strips. Finally, we discuss dramatic enhancement of the anisotropy of the flux patterns due to specific dynamics. In this way we demonstrate that the combination of the linear stability analysis with the numerical approach provides an efficient framework for understanding the ultra-fast coupled nonlocal dynamics of electromagnetic fields and dissipation in superconductor films.

• Laliena, Carlos; Qureishy, Thomas; Martínez, Elena; Navarro, Rafael; Mikheenko, Pavlo & Johansen, Tom Henning [Show all 7 contributors for this article] (2017). Effect of ball milling on the local magnetic flux distribution and microstructure of in situ Fe/MgB2 conductors. Journal of Alloys and Compounds. ISSN 0925-8388. 717, p. 164–170. doi: 10.1016/j.jallcom.2017.05.083. Full text in Research Archive Show summary

  The effects of the precursor milling energy on the superconducting and microstructural homogeneity of Fe-sheathed MgB2 monocore wires and tapes have been investigated. The conductors were produced by the powder-in-tube method using drawing and rolling deformation methods and in situ reaction. Combined magneto-optical, structural and magnetization measurements were performed on MgB2 superconducting tapes prepared from differently milled precursors revealing hidden mechanisms controlling their critical current density. Local degradation of the superconducting properties observed in some analysed conductors has been identified and correlated with microstructural observations.

• Jung, Soon-Gil; Shin, Soohyeon; Jang, Harim; Mikheenko, Pavlo; Johansen, Tom Henning & Park, Tuson (2017). Effects of magnetic impurities on upper critical fields in the high-T c superconductor La-doped CaFe2As2. Superconductors Science and Technology. ISSN 0953-2048. 30:085009(8), p. 1–8. doi: 10.1088/1361-6668/aa766c. Full text in Research Archive Show summary

  We investigate the effects of magnetic impurities on the upper critical field (μ 0 H c2) in La-doped CaFe2As2 (LaCa122) single crystals. The magnetic field dependency of the superconducting transition temperature (T c) for LaCa122 is rapidly suppressed at low fields up to ~1 kOe despite its large μ 0 H c2(0) value on the order of tens of Tesla, resulting in a large positive curvature of μ 0 H c2(T) near T c. The magnetization hysteresis (M–H) loop at temperatures above T c shows a ferromagnetic-like signal and the M(H) value rapidly increases with increasing magnetic field up to ~1 kOe. Taken together with the linear suppression of T c with the magnetization in the normal state, these results suggest that the large upward curvature of μ 0 H c2(T) near T c in La-doped CaFe2As2 mainly originates from the suppression of superconductivity due to the presence of magnetic impurities. © 2017 IOP Publishing

• Colauto, Fabiano; Carmo, D.; Andrade, AMH de; Oliveira, AAM; Ortiz, w. a. & Johansen, Tom Henning (2017). Anisotropic thermomagnetic avalanche activity in field-cooled superconducting films. Physical review B (PRB). ISSN 2469-9950. 96(6), p. 1–5. doi: 10.1103/PhysRevB.96.060506. Full text in Research Archive
• Brisbois, J.; Gladilin, V.N.; Tempere, J.; Devreese, J.T.; Moshchalkov, V. V. & Colauto, Fabiano [Show all 14 contributors for this article] (2017). Flux penetration in a superconducting film partially capped with a conducting layer. Physical review B (PRB). ISSN 2469-9950. 95(9). doi: 10.1103/PhysRevB.95.094506. Full text in Research Archive
• Lopes, R.F.; Carmo, D.; Colauto, Fabiano; Ortiz, W. A.; Andrade, Adnei Melges H. De & Johansen, Tom Henning [Show all 8 contributors for this article] (2017). Spin texture on top of flux avalanches in Nb/Al2O3/Co thin film heterostructures. Journal of Applied Physics. ISSN 0021-8979. 121(1). doi: 10.1063/1.4973529. Full text in Research Archive
• Shabbir, B.; Huang, H.; Yao, Chao; Ma, Y.; Dou, S. X. & Johansen, Tom Henning [Show all 8 contributors for this article] (2017). Evidence for superior current carrying capability of iron pnictide tapes under hydrostatic pressure. PHYSICAL REVIEW MATERIALS. 1(4). doi: 10.1103/PhysRevMaterials.1.044805. Full text in Research Archive
• Hashimoto, Yusuke; Daimon, Shunsuke; Iguchi, Ryo; Oikawa, Yasuyuki; Shen, Ka & Sato, Koji [Show all 15 contributors for this article] (2017). All-optical observation and reconstruction of spin wave dispersion. Nature Communications. 8. doi: 10.1038/ncomms15859. Full text in Research Archive
• Qureishy, Thomas; Zhao, Yue; Xu, Yan; Vestgården, Jørn Inge; Johansen, Tom Henning & Grivel, Jean-Claude [Show all 8 contributors for this article] (2017). Magnetic flux channelling in YBa2Cu3O7-δ films grown by a chemical solution deposition technique on vicinal and non-vicinal substrates. Advanced Materials Letters. ISSN 0976-3961. 8, p. 1204–1210. doi: 10.5185/amlett.2017.1474. Full text in Research Archive Show summary

  Magneto-optical imaging of YBa2Cu3O7-δ films with high critical current density, synthesized by a cost-effective metal organic decomposition technique reveals inhomogeneous flux penetration in the specimens in the form of thin parallel lines. The origin of such a stripy pattern and its dependence on the sample preparation conditions and state of substrate is discussed. The stripes reflect accumulation of planar defects forming parallel lines of reduced in-plane critical current density, jc , perpendicular to planar defects and enhanced jc parallel to them. Such channel-like reduction and corresponding enhancement of jc is especially expressed in a sample deposited on vicinal substrate, which, as a consequence, demonstrates global temperature-dependent in-plane anisotropy with an anisotropy ratio up to 2.4. The directional enhancement of critical current density due to planar defects could be beneficial for practical use of superconducting films.

• Qureishy, Thomas; Laliena, Carlos; Martínez, Elena; Qviller, Atle Jorstad; Vestgården, Jørn Inge & Johansen, Tom Henning [Show all 8 contributors for this article] (2017). Dendritic flux avalanches in a superconducting MgB2 tape. Superconductors Science and Technology. ISSN 0953-2048. doi: 10.1088/1361-6668/aa9244. Full text in Research Archive Show summary

  Tapes of MgB2 with high critical current have a significant technological potential, but can experience operational breakdown due to thermomagnetic instabilities. Such events are routinely registered by magnetisation measurements, but were never observed by direct imaging techniques. Here we report magneto-optical imaging visualisation of a tape with reduced thickness and enhanced critical current density. The spatial structure of the thermomagnetic avalanche events was resolved, and the reproducibility and nucleation thresholds were determined. Avalanches appearing at low fields are small intrusions at the tape edges, while larger fields create more extensive avalanches having dendritic structures similar to those observed in thin-film superconductors. In contrast to dendritic avalanches in thin films, the avalanches in the tapes show reproducibility to a larger extent.

• Martinez-Pedrero, Fernando; Tierno, Pietro; Johansen, Tom Henning & Straube, Arthur V. (2016). Regulating wave front dynamics from the strongly discrete to the continuum limit in magnetically driven colloidal systems. Scientific Reports. 6. doi: 10.1038/srep19932. Full text in Research Archive
• Tierno, Pietro; Johansen, Tom Henning & Sancho, Jose M. (2016). A Tunable Magnetic Domain Wall Conduit Regulating Nanoparticle Diffusion. Nano Letters. ISSN 1530-6984. 16(8), p. 5169–5175. doi: 10.1021/acs.nanolett.6b02112. Full text in Research Archive
• Carmo, D.; Colauto, F.; Andrade, AMH de; Oliveira, AAM; Ortiz, W. A. & Johansen, Tom Henning (2016). Controllable injector for local flux entry into superconducting films. Superconductors Science and Technology. ISSN 0953-2048. 29(9). doi: 10.1088/0953-2048/29/9/095003. Full text in Research Archive
• Baruch-El, E.; Baziljevich, Michail; Shapiro, B. Ya.; Johansen, Tom Henning; Shaulov, A. & Yeshurun, Y. (2016). Dendritic flux instabilities in YBa2Cu3O7-x films: Effects of temperature and magnetic field ramp rate. Physical Review B. Condensed Matter and Materials Physics. ISSN 1098-0121. 94(5). doi: 10.1103/PhysRevB.94.054509. Full text in Research Archive
• Mikheenko, Pavlo; Vestgården, Jørn Inge; Chaudhuri, Saumyadip; Maasilta, Ilari J.; Galperin, Yuri & Johansen, Tom Henning (2016). Metal frame as local protection of superconducting films from thermomagnetic avalanches. AIP Advances. 6:032304. doi: 10.1063/1.4943549. Full text in Research Archive Show summary

  Thermomagnetic avalanches in superconducting films propagating extremely fast while forming unpredictable patterns, represent a serious threat for the performance of devices based on such materials. It is shown here that a normal-metal frame surrounding a selected region inside the film area can provide efficient protection from the avalanches during their propagation stage. Protective behavior is confirmed by magneto-optical imaging experiments on NbN films equipped with Cu and Al frames, and also by performing numerical simulations. Experimentally, it is found that while conventional flux creep is not affected by the frames, the dendritic avalanches are partially or fully screened by them. The level of screening depends on the ratio of the sheet conductance of the metal and the superconductor in the resistive state, and for ratios much larger than unity the screening is very efficient.

• Martinez-Pedrero, Fernando; Massana-Cid, Helena; Ziegler, Till; Johansen, Tom Henning; Straube, Arthur V. & Tierno, Pietro (2016). Bidirectional particle transport and size selective sorting of Brownian particles in a flashing spatially periodic energy landscape. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 18(38), p. 26353–26357. doi: 10.1039/c6cp05599k. Full text in Research Archive
• Vestgården, Jørn Inge; Galperin, Yuri & Johansen, Tom Henning (2016). Oscillatory regimes of the thermomagnetic instability in superconducting films. Physical Review B. Condensed Matter and Materials Physics. ISSN 1098-0121. doi: 10.1103/PhysRevB.93.174511. Full text in Research Archive Show summary

  The stability of superconducting films with respect to oscillatory precursor modes for thermomagnetic avalanches is investigated theoretically. The results for the onset threshold show that previous treatments of nonoscillatory modes have predicted much higher thresholds. Thus, in film superconductors, oscillatory modes are far more likely to cause thermomagnetic breakdown. This explains the experimental fact that flux avalanches in film superconductors can occur even at very small ramping rates of the applied magnetic field. Closed expressions for the threshold magnetic field and temperature, as well oscillation frequency, are derived for different regimes of the oscillatory thermomagnetic instability.

• Colauto, Fabiano; Motta, Maycon; Palau, A.; Blamire, M.G.; Johansen, Tom Henning & Ortiz, Wilson Aires (2015). First observation of flux avalanches in a-MoSi superconducting thin films. IEEE Transactions on Applied Superconductivity (TAS). ISSN 1051-8223. 25(3). doi: 10.1109/TASC.2014.2376183. Full text in Research Archive
• Martinez-Pedrero, Farnando; Straube, Arthur V.; Johansen, Tom Henning & Tierno, Pietro (2015). Functional colloidal micro-sieves assembled and guided above a channel-free magnetic striped film. Lab on a Chip. ISSN 1473-0197. doi: 10.1039/C5LC00067J. Full text in Research Archive
• Carmo, D.; Colauto, F.; Andrade, Adnei Melges H. De; Oliveira, Adriana A.M; Ortiz, Wilson Aires & Johansen, Tom Henning (2015). Trapping flux avalanches in Nb films by circular stop-holes of different size. IEEE Transactions on Applied Superconductivity (TAS). ISSN 1051-8223. 25(3). doi: 10.1109/TASC.2014.2364733. Full text in Research Archive
• Mikheenko, Pavlo; Johansen, Tom Henning; Chaudhuri, S.; Maasilta, IJ & Galperin, Yuri (2015). Ray optics behavior of flux avalanche propagation in superconducting films. Physical Review B. Condensed Matter and Materials Physics. ISSN 1098-0121. 91(6). doi: 10.1103/PhysRevB.91.060507. Full text in Research Archive Show summary

  Experimental evidence of wave properties of dendritic flux avalanches in superconducting films is reported. Using magneto-optical imaging the propagation of dendrites across boundaries between a bare NbN film and areas coated by a Cu layer was visualized, and it was found that the propagation is refracted in full quantitative agreement with Snell’s law. For the studied film of 170 nm thickness and a 0.9 μmthick metal layer, the refractive index was close to n = 1.4. The origin of the refraction is believed to be caused by the dendrites propagating as an electromagnetic shock wave, similar to damped modes considered previously for normal metals. The analogy is justified by the large dissipation during the avalanches raising the local temperature significantly. Additional time-resolved measurements of voltage pulses generated by segments of the dendrites traversing an electrode confirm the consistency of the adopted physical picture.

• Vestgården, Jørn Inge; Colauto, Fabiano; Andrade, AMH de; Oliveira, AAM; Ortiz, W. A. & Johansen, Tom Henning (2015). Cascade dynamics of thermomagnetic avalanches in superconducting films with holes. Physical Review B. Condensed Matter and Materials Physics. ISSN 1098-0121. doi: 10.1103/PhysRevB.92.144510. Full text in Research Archive Show summary

  The submicrosecond dynamics of thermomagnetic avalanches in superconducting films with nonconducting holes (antidots) is considered. When such an avalanche reaches a hole, it is quickly filled with magnetic flux, and often its rim becomes unstable and a second avalanche is nucleated. In this work the time- and space-resolved behavior of such cascading avalanche behavior is determined using numerical simulations. Results are presented for films with holes of different shape. It is found that holes with sharp corners are those that most frequently create secondary avalanches, and they tend to nucleate in corners. Magneto-optical imaging of Nb films patterned with the same set of holes strongly supports the numerical results.

• Tierno, Pietro; Johansen, Tom Henning & Fischer, T. M. (2014). Fast and rewritable colloidal assembly via field synchronized particle swapping. Applied Physics Letters. ISSN 0003-6951. 104(17). doi: 10.1063/1.4874839. Full text in Research Archive
• Mikheenko, Pavlo & Johansen, Tom Henning (2014). Smart superconducting grid. Energy Procedia. 58, p. 73–78. doi: 10.1016/j.egypro.2014.10.411. Full text in Research Archive
• Baziljevich, Michael; Baruch-El, E.; Johansen, Tom Henning & Yeshurun, Y. (2014). Dendritic instability in YBCO films triggered by transient magnetic fields. Applied Physics Letters. ISSN 0003-6951. 105(1). doi: 10.1063/1.4887374. Full text in Research Archive
• Vestgården, Jørn Inge; Mikheenko, Pavlo; Galperin, Yuri & Johansen, Tom Henning (2014). Inductive braking of thermomagnetic avalanches in superconducting films. Superconductors Science and Technology. ISSN 0953-2048. 27(5). doi: 10.1088/0953-2048/27/5/055014. Full text in Research Archive
• Motta, Maycon; Colauto, Fabiano; Vestgården, Jørn Inge; Fritzsche, Joachim; Timmermans, Matias & Cuppens, Jo [Show all 13 contributors for this article] (2014). Controllable morphology of flux avalanches in microstructured superconductors. Physical Review B. Condensed Matter and Materials Physics. ISSN 1098-0121. 89:135408(13). doi: 10.1103/PhysRevB.89.134508. Full text in Research Archive
• Borroto, A; Rio, L Del; Arronte, Miguel; Johansen, Tom Henning & Altshuler, Ernesto (2014). Modeling transport properties of inhomogeneous superconductor-metal composites. Applied Physics Letters. ISSN 0003-6951. 105(20). doi: 10.1063/1.4902357. Full text in Research Archive
• Baruch-El, E.; Baziljevich, Michael; Johansen, Tom Henning & Yeshurun, Yosef (2014). Substrate Influence on Dendritic Flux Instability in YBCO Thin Films. Journal of Superconductivity and Novel Magnetism. ISSN 1557-1939. 28(2), p. 379–382. doi: 10.1007/s10948-014-2723-9. Full text in Research Archive
• Kytin, V.G; Kulbachinskii, V.A; Reukova, O.V; Galperin, Yuri; Johansen, Tom Henning & Diplas, Spyridon [Show all 7 contributors for this article] (2014). Conducting properties of In2O3:Sn thin films at low temperatures. Applied Physics A: Materials Science & Processing. ISSN 0947-8396. 114(3), p. 957–964. doi: 10.1007/s00339-013-7799-8. Full text in Research Archive Show summary

  Electrical conductivity, Hall effect and magnetoresistance of In2O3:Sn thin films deposited on a glass substrates at different temperatures and oxygen pressures, have been investigated in the temperature range 4.2–300 K. The observed temperature dependences of resistivity for films deposited at 230 °C as well as at nominally room temperatures were typical for metallic transport of electrons except temperature dependence of resistivity of the In2O3:Sn film deposited in the oxygen deficient atmosphere. The electrical measurements were accompanied by AFM and SEM studies of structural properties, as well as by XPS analysis. It is established that changes of morphology and crystallinity of ITO films modify the low-temperature behavior of resistivity, which still remains typical for metallic transport. This is not the case for the oxygen deficient ITO layer. XPS analysis shows that grown in situ oxygen deficient ITO films have enhanced DOS between the Fermi level and the valence band edge. The extra localized states behave as acceptors leading to a compensation of n-type ITO. That can explain lower n-type conductivity in this material crossing over to a Mott-type hopping at low temperatures. Results for the low temperature measurements of stoichiometric ITO layers indicate that they do not show any trace of metal-to-insulator transition even at 4.2 K. We conclude that, although ITO is considered as a highly doped wide-band gap semiconductor, its low-temperature properties are very different from those of conventional highly doped semiconductors.

• Zadorosny, Rafael; Colauto, Fabiano; Motta, Maycon; Johansen, Tom Henning; Dinner, Rafael & Blamire, Mark [Show all 10 contributors for this article] (2013). Morphology of Flux Avalanches in Patterned Superconducting Films. Journal of Superconductivity and Novel Magnetism. ISSN 1557-1939. 26(6), p. 2285–2288. doi: 10.1007/s10948-012-1429-0. Full text in Research Archive
• Mikheenko, Pavlo; Yurchenko, Vitaliy; Cardwell, David A.; Shi, Yunhua & Johansen, Tom Henning (2013). Magneto-optical imaging of superconductors for liquid hydrogen applications. Journal of Superconductivity and Novel Magnetism. ISSN 1557-1939. 26(5), p. 1499–1502. doi: 10.1007/s10948-012-2033-z. Full text in Research Archive
• Vestgården, Jørn Inge; Mikheenko, Pavlo; Galperin, Yuri & Johansen, Tom Henning (2013). Nonlocal electrodynamics of normal and superconducting films. New Journal of Physics. 15. doi: 10.1088/1367-2630/15/9/093001. Full text in Research Archive
• Colauto, Fabiano; Vestgarden, Jørgen; Andrade, AMH de; Oliveira, AAM; Ortiz, WA & Johansen, Tom Henning (2013). Limiting thermomagnetic avalanches in superconducting films by stop-holes. Applied Physics Letters. ISSN 0003-6951. 103(3). doi: 10.1063/1.4813908. Full text in Research Archive
• Borroto, Alejandro; Rio, Lenin Del; Altshuler, Ernesto; Arronte, Miguel; Mikheenko, Pavlo & Qviller, Atle Jorstad [Show all 7 contributors for this article] (2013). Local transport in multi-filamentary superconductors: longitudinal versus transverse dissipation. Superconductors Science and Technology. ISSN 0953-2048. 26(11:115004). doi: 10.1088/0953-2048/26/11/115004. Full text in Research Archive
• Johansen, Tom Henning; Pan, Alexey & Galperin, Yuri (2013). Exact asymptotic behavior of magnetic stripe domain arrays. Physical Review B. Condensed Matter and Materials Physics. ISSN 1098-0121. 87(6). doi: 10.1103/PhysRevB.87.060402. Full text in Research Archive
• Tierno, Pietro; Johansen, Tom Henning & Sancho, J.M. (2013). Unconventional dynamic hysteresis in a periodic assembly of paramagnetic colloids. Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. ISSN 1539-3755. 87(6). doi: 10.1103/PhysRevE.87.062301. Full text in Research Archive
• Yurchenko, Vitaliy; Ilin, K; Meckbach, JM; Siegel, M; Qviller, Atle Jorstad & Galperin, Yuri [Show all 7 contributors for this article] (2013). Thermo-magnetic stability of superconducting films controlled by nanomorphology. Applied Physics Letters. ISSN 0003-6951. 102(25). doi: 10.1063/1.4812484. Full text in Research Archive
• Vestgården, Jørn Inge; Galperin, Yuri & Johansen, Tom Henning (2013). The Thermomagnetic Instability in Superconducting Films with Adjacent Metal Layer. Journal of Low Temperature Physics. ISSN 0022-2291. 173(5-6), p. 303–326. doi: 10.1007/s10909-013-0899-1. Full text in Research Archive
• Motta, M; Colauto, F; Ortiz, WA; Fritzsche, J.; Cuppens, J. & Gillijns, W. [Show all 10 contributors for this article] (2013). Enhanced pinning in superconducting thin films with graded pinning landscapes. Applied Physics Letters. ISSN 0003-6951. 102(21). doi: 10.1063/1.4807848. Full text in Research Archive
• Mikheenko, Pavlo; Qviller, Atle Jorstad; Vestgården, Jørn Inge; Chaudhuri, S.; Maasilta, IJ & Galperin, Yuri [Show all 7 contributors for this article] (2013). Nanosecond voltage pulses from dendritic flux avalanches in superconducting NbN films. Applied Physics Letters. ISSN 0003-6951. 102(2), p. 022601-1–022601-3. doi: 10.1063/1.4775693. Full text in Research Archive Show summary

  Combined voltage and magneto-optical study of magnetic flux flow in superconducting NbN films is reported. The nanosecond-scale voltage pulses appearing during thermomagnetic avalanches have been recorded in films partially coated by a metal layer. Simultaneous magneto-optical imaging and voltage measurements allowed the pulses to be associated with individual flux branches penetrating the superconductor below the metal coating. From detailed characteristics of pulse and flux branches, the electrical field in the superconductor is found to be in the range of 5-50 kV/m, while the propagation speed of the avalanche during its final stage is found to be close to 5 km/s. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.

• Vestgården, Jørn Inge; Shantsev, Daniil; Galperin, Yuri & Johansen, Tom Henning (2013). The diversity of flux avalanche patterns in superconducting films. Superconductors Science and Technology. ISSN 0953-2048. 26(5). doi: 10.1088/0953-2048/26/5/055012. Full text in Research Archive
• Motta, M; Colauto, F; Johansen, Tom Henning; Dinner, RB; Blamire, M.G. & Ataklti, G. W. [Show all 9 contributors for this article] (2012). Flux avalanches triggered by AC magnetic fields in superconducting thin films. Physica. C, Superconductivity. ISSN 0921-4534. 479, p. 134–136. doi: 10.1016/j.physc.2011.12.030. Full text in Research Archive

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• Colauto, Fabiano; Andrade, Adnei Melges H. De; Carmo, D.; Oliveira, Aria M.; Ortiz, Wilson Aires & Galperin, Yuri [Show all 7 contributors for this article] (2018). Field-induced anisotropy in Nb films with different thicknesses. Full text in Research Archive
• Qureishy, Thomas; Laliena, Carlos; Martínez, Elena; Qviller, Atle Jorstad; Vestgården, Jørn Inge & Johansen, Tom Henning [Show all 8 contributors for this article] (2018). Magneto-optical imaging of dendritic flux avalanches in a superconducting MgB2 tape. Full text in Research Archive
• Motta, M.; Colauto, Fabiano; Johansen, Tom Henning; Moshchalkov, Victor V.; Silhanek, Alejandro V. & Ortiz, w. a. (2017). Magnetic Imaging of AC Susceptibility in Superconducting Thin Films. Full text in Research Archive
• Johansen, Tom Henning (2017). Magneto-optical imaging: How to view magnetism with your own eyes. Full text in Research Archive
• Mikheenko, Pavlo; Vestgården, Jørn Inge; Tyse, Knut & Johansen, Tom Henning (2017). Magneto-optical imaging of superconductors: science and applications. Full text in Research Archive
• Qureishy, Thomas; Zhao, Yue; Xu, Yan; Vestgården, Jørn Inge; Johansen, Tom Henning & Grivel, Jean-Claude [Show all 8 contributors for this article] (2017). Visualisation of magnetic flux in high-quality YBCO films synthesized by cost-effective environmental-friendly techniques. Full text in Research Archive
• Martínez, Elena; Laliena, Carlos; Qureishy, Thomas; Navarro, Rafael; Mikheenko, Pavlo & Johansen, Tom Henning [Show all 7 contributors for this article] (2017). Magneto-optical, microstructural and magnetization measurements of in situ Fe/MgB2 conductors made from ball-milled precursor. Full text in Research Archive
• Johansen, Tom Henning (2017). Magneto-optical imaging - How to see magnetism with your own eyes. Full text in Research Archive
• Johansen, Tom Henning; Galperin, Yuri; Baziljevich, Michail & Mikheenko, Pavlo (2017). Magneto-optical Imaging - How to See magnetism with your own eyes. Full text in Research Archive
• Lopes, R. F.; Carmo, D.; Colauto, F; Ortiz, WA; Johansen, Tom Henning & Andrade, AMH de (2017). Spin textures. Full text in Research Archive
• Qureishy, Thomas; Zhao, Yue; Xu, Y; Vestgården, Jørn Inge; Johansen, Tom Henning & Grivel, Jean-Claude [Show all 8 contributors for this article] (2016). Magnetic flux channelling in YBa2Cu3O7-δ films. Full text in Research Archive
• Johansen, Tom Henning; Mikheenko, Pavlo; Maasilta, IJ; Chaudhuri, S. & Galperin, Yuri (2015). Snell's law behaviour of flux avalanche propagation in superconducting films. Full text in Research Archive
• Galperin, Yuri; Mikheenko, Pavlo; Johansen, Tom Henning; Chaudhuri, S. & Maasilta, IJ (2015). Ray optics behavior of flux avalanche propagation in superconducting films. Full text in Research Archive
• Mikheenko, Pavlo; Vestgården, Jørn Inge; Chaudhuri, S.; Maasilta, IJ; Galperin, Yuri & Cardwell, David A. [Show all 14 contributors for this article] (2015). Magneto-Optical Imaging: a tool for fundamental physics and applications of superconductivity. Full text in Research Archive
• Qureishy, Thomas Håbu; Tyse, Knut; Zhao, Yue; Vestgården, Jørn Inge; Grivel, Jean-Claude & Johansen, Tom Henning [Show all 7 contributors for this article] (2015). Local critical current density in YBa2Cu3O7-δ films. Full text in Research Archive
• Galperin, Yuri; Johansen, Tom Henning & Vestgården, Jørn Inge (2014). Magnetic dendrites in superconductors. Full text in Research Archive
• Mikheenko, Pavlo; Vestgården, Jørn Inge; Chaudhuri, S.; Maasilta, IJ; Galperin, Yuri & Johansen, Tom Henning (2014). Complex flux flow in superconducting films. Full text in Research Archive
• Ortiz, w. a.; Johansen, Tom Henning; Motta, Maycon; Colauto, Fabiano; Moshchalkov, Victor V. & Vestgården, J. I. (2014). Critical current enhancement and guidance of flux avalanches in microstructured superconducting films. Full text in Research Archive
• Colauto, Fabiano; Ortiz, w. a.; Vestgården, J. I. & Johansen, Tom Henning (2014). Limiting thermomagnetic avalanches in superconducting films by stop-holes. Full text in Research Archive
• Motta, Maycon; Colauto, Fabiano; Moshchalkov, Victor V.; Silhanek, Alejandro V. & Johansen, Tom Henning (2014). Geometry-dependent critical currents and guidance of flux avalanches in patterned superconducting thin films. Full text in Research Archive
• Ortiz, w. a.; Colauto, Fabiano; Motta, Maycon & Johansen, Tom Henning (2014). First observation of flux avalanches in a-MoSi superconducting thin films. Full text in Research Archive
• Johansen, Tom Henning; Galperin, Yuri; Vestgården, Jørn Inge & Mikheenko, Pavlo (2013). Lightning in superconductors. Full text in Research Archive
• Johansen, Tom Henning (2013). Occasional address. Full text in Research Archive
• Mikheenko, Pavlo; Qviller, Atle Jorstad; Vestgården, Jørn Inge; Chaudhuri, S.; Maasilta, IJ & Galperin, Yuri [Show all 7 contributors for this article] (2013). Magnetic flux avalanches in superconducting films. Full text in Research Archive
• Mikheenko, Pavlo; Mikheenko, Iryna; Jenkins, P; Attard, G; Creamer, Neil & Williams, A [Show all 10 contributors for this article] (2013). Biomembranes for recovery of precious metals. Full text in Research Archive
• Baziljevich, Michael; Baruch-El, Elran; Barness, Doron; Sinvani, Moshe; Perel, Eliezer & Shaulov, Avner [Show all 8 contributors for this article] (2013). High speed magneto-optical imaging of flux dynamics. Full text in Research Archive
• Ortiz, W. A.; Motta, M.; Colauto, Fabiano; Vestgården, J. I.; Johansen, Tom Henning & Moshchalkov, V. V. [Show all 7 contributors for this article] (2013). Guidance and morphology of flux avalanches in superconducting films decorated with lattices of antidots. Full text in Research Archive
• Silhanek, A. V.; Motta, M.; Colauto, F.; Fritsche, J.; Vestgården, Jørn Inge & Moshchalkov, V. V. [Show all 8 contributors for this article] (2013). Current crowding effects in nanostructured superconductors. Full text in Research Archive
• Motta, Maycon; Colauto, Fabiano; Fritsche, J.; Moshchalkov, V. V.; Johansen, Tom Henning & Sanchez, A. [Show all 8 contributors for this article] (2013). Enhanced critical current in superconducting thin films with graded pinning landscapes. Full text in Research Archive
• Galperin, Yuri & Johansen, Tom Henning (2012). Avalanche penetration of magnetic flux into supercvonducting films. Full text in Research Archive

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