Speaker: Neil Campbell, Physics PhD Graduate Student
Abstract: While the Hall effect has been around for well over a century now, its utility as a probe of conducting, and especially magnetic, materials is as high as ever. As thin-film synthesis techniques continue expanding the boundaries of what materials are possible to create the Hall effect allows experimental probing of new and old phenomena in these films. Currently, Hall effects resulting from topological properties of materials are of high interest, be they from a topologically-protected band structure or a Berry phase that results from an antiferromagnetic spin arrangement. It was the goal of my research many times to observe such an effect, and in this regard the subsequent chapters could be viewed as a litany of failure. However, the investigations pursued did result in better understanding of the materials and in some cases, like in Pr2Ir2O7 finding new interesting phenomena. In this case I report that a broken symmetry as a result of growing the material in thin-film form results in a spin Hall effect that persists to much higher temperatures. Such a result suggests a road map for increasing the temperatures at which some low-temperature phenoma are observed. In SrIrO3 after pursuing a topolgical band structure, I ended up showing the lack of magnetic ordering in distorted Perovskite SrIrO3, which many researchers had presumed to exist. In the Mn3GaN chapters I use other magnetic characterizations and analysis to show the impact of heterostructring on magnetic anisotropy in a way that demonstrates a path for manipulating hard ferrimagnets to be amenable for spintronics. And finally use the well-known phenomenon of exchange bias to show how to break the degeneracy of antiferromagnetic domains, a problem that currently plagues many promising spintronic candidate materials.