Abstract
Functional properties of complex oxides are governed not only by their crystal structure and chemistry, but also by microstructure, interfaces, and local strain fields. Using hexagonal rare-earth oxides as model systems, I will show how advanced characterization methods ranging from scanning probe microscopy to atom probe tomography can uncover these relationships across different length scales. I will first discuss how microstructure, interfaces, strain, and local chemistry influence ferroelectric order and domain formation in hexagonal manganites. Extending from ferroelectric to magnetic order, I will then explain how rare-earth chemistry and competing magnetic interactions can be used to tune magnetic ground states from antiferromagnetic order to frustrated magnetism, leading to large magnetocaloric effects across temperatures ranging from tens of kelvin to the sub-kelvin regime. These concepts underpin the COOLCATCH and FROST projects, targeting functional oxides for energy-efficient cryogenic cooling for quantum technologies and hydrogen liquefaction.