Successful defence of James Taylor

Congratulations to James Taylor !

September 30, 2020

Title: "Epitaxial thin films of the noncollinear antiferromagnets Mn3Ir and Mn3Sn for topological spintronic applications"

Abstract

In this thesis, we prepare epitaxial thin films of the noncollinear antiferromagnets Mn3Ir and Mn3Sn, via magnetron sputtering. Their crystal structure is characterized by x-ray diffraction and transmission electron microscopy. Measurements of their magnetic properties, using vibrating sample magnetometry and x-ray magnetic circular dichroism, reveal the important role of uncompensated Mn moments. To assess the thin films’ suitability for topological spintronic applications, we study magnetotransport in lithographically fabricated devices. In the case of Mn3Sn, we measure Berry curvature driven anomalous Hall effect at 300 K, with a magnitude of σxy(µ0H = 0 T) = 21 Ω−1 cm−1 , in thin films down to 30 nm. On subsequent cooling to below its transition into a glassy ferromagnetic state, we observe a change to a topological Hall effect. We attribute this to chiral domain walls in our Mn3Sn films, and observe that their spin configuration depends on magnetic-field cooling condition.

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