Anomalous Hall Effect in Mn-Sn Thin Films - Correlation with Crystal Structure

Abstract

Non-collinear antiferromagnets such as D019-Mn3Sn have attracted much attention owing to their large anomalous Hall effect (AHE) originating from non-vanishing Berry curvature [1-5]. We recently reported a growth of epitaxial D019-Mn3Sn thin films with various orientations by sputtering, where anisotropic AHE was observed [5]. To realize functional devices harnessing the unique features of this material system, it is necessary to clarify the correlation of the physical properties with various factors of thin film. Here, we study the correlation between AHE and crystal structure of Mn-Sn alloy film by changing post-annealing temperature (Ta) and Mn-Sn composition. We prepare two series of Mn3+xSn1-x thin films which are deposited on MgO(110) substrate by sputtering. The first series have a fixed x = +0.06 and Ta is changed from 300 to 600oC. The second series have various x (-0.35 ~ +0.32) with a fixed Ta = 500oC. Crystal structures are characterized by X-ray diffraction (XRD). Transport measurement is performed for microfabricated Hall devices. From XRD measurement, we find that dominant phase of Mn-Sn changes from Mn1.75Sn to D019-Mn3Sn as Ta increases (series 1), and changes from Mn3Sn2 to D019-Mn3Sn as x increases (series 2) in the studied range. Transport measurement for the series 1 reveals that appearance of AHE coincides with the formation of D019-Mn3Sn and the magnitude increases with Ta [Fig. 1]. Meanwhile, for the series 2, the largest AHE is obtained at around the stoichiometric composition [Fig. 2]. We here note that the two series are prepared at different times, leading to different magnitude of AHE. From a comparison with XRD results, we find that magnitude of AHE is well explained by multiple factors of crystalline structure including proportion of D019-Mn3Sn crystallite, crystalline orientation, and the order parameter. The obtained results provide an important insight to deepen the physics of non-collinear antiferromagnet and to realize new-functional devices. This work is partly supported by JSPS Kakenhi No. 19H05622 and No. 19J13405.