Ryan Need | Search arXiv

arXiv2020

Anomalous Hall and Nernst effects in epitaxial films of topological kagome magnet Fe3Sn2

The topological kagome magnet (TKM) Fe3Sn2 exhibits unusual topological properties, flat electronic bands, and chiral spin textures, making it an exquisite materials platform to explore the interplay between topological band structure, strong electron correlations, and magnetism. Here we report the first synthesis of high-quality epitaxial (0001) Fe3Sn2 films with large intrinsic anomalous Hall effect close to that measured in bulk single crystals. In addition, we measured a large, anisotropic anomalous Nernst coefficient Syx of 1.26 {\mu}V/K, roughly 2-5x greater than that of common ferromagnets, suggesting the presence of Berry curvature sources near the Fermi level in this system. Crucially, the realization of high-quality Fe3Sn2 films opens the door to explore emergent interfacial physics and create novel spintronic devices based on TKMs by interfacing Fe3Sn2 with other quantum materials and by nanostructure patterning.

cond-mat.mtrl-sci↗

arXiv2018

Spin Seebeck imaging of spin-torque switching in antiferromagnetic Pt/NiO heterostructures

As electrical control of N\'eel order opens the door to reliable antiferromagnetic spintronic devices, understanding the microscopic mechanisms of antiferromagnetic switching is crucial. Spatially-resolved studies are necessary to distinguish multiple nonuniform switching mechanisms; however, progress has been hindered by the lack of tabletop techniques to image the N\'eel order. We demonstrate spin Seebeck microscopy as a sensitive, table-top method for imaging antiferromagnetic order in thin films, and apply this technique to study spin-torque switching in NiO/Pt and Pt/NiO/Pt heterostructures. We establish the interfacial antiferromagnetic spin Seebeck effect in NiO as a probe of surface N\'eel order, resolving antiferromagnetic spin domains within crystalline twin domains. By imaging before and after applying current-induced spin torque, we resolve spin domain rotation and domain wall motion, acting simultaneously. We correlate the changes in spin Seebeck images with electrical measurements of the average N\'eel orientation through the spin Hall magnetoresistance, confirming that we image antiferromagnetic order.

cond-mat.mtrl-sci↗