Nanoscale characterization of magnetic microstructure in Gd₃Fe₅O₁₂

A key barrier to the understanding of magnetic phenomena and design of functional magnetic materials is the limited scope of nanoscale characterization of magnetic microstructure. We utilize scanning x-ray diffraction microscopy to image the magnetic domain morphology in rare-earth iron garnets as a function of temperature using an x-ray wave plate and zone plate focusing optics to generate a 100 nm beam of circularly polarized synchrotron light. Rare earth iron garnets such as Gd₃Fe₅O₁₂ are magnetic systems that can exhibit spin Seebeck effect (SSE) voltage generation with an efficiency that could depend on the morphology of the magnetic domain structures. We have obtained linear and circular x-ray magnetic dichroism maps of the micron- to submicron-scale distributions of magnetic domains recorded in a prototype SSE device composed of epitaxial layers of Gd₃Fe₅O₁₂ capped with 10 nm of Pt for temperatures ranging from 4 K to 250 K. These results bring insight into the relationship between the temperature-dependent magnetic domain morphology and the efficiency of SSE devices based on rare-earth iron garnets.