Tunable magnetic and transport properties of Mn3Ga thin films on Ta/Ru seedlayer

TL;DR

This study demonstrates how tuning the seed layer in Mn3Ga thin films can control their magnetic phases and Hall effects, revealing complex behaviors linked to spin frustration with potential spintronic applications.

Contribution

It introduces a method to control phase and magnetic properties of Mn3Ga films via seed layer engineering, highlighting the relationship between structure and anomalous Hall effects.

Findings

Tetragonal and hexagonal phases can be selectively stabilized by seed layer composition.

Large anomalous Hall resistivity observed in mixed-phase samples.

Sign reversal of Hall effect occurs above 200K in pure hexagonal phase.

Abstract

Hexagonal D019-type Mn3Z alloys that possess large anomalous and topological-like Hall effects have attracted much attention due to their great potential in the antiferromagnetic spintronic devices. Here, we report the preparation of Mn3Ga film in both tetragonal and hexagonal phases with a tuned Ta/Ru seed layer on the thermally oxidized Si substrate. A large coercivity together with a large anomalous Hall resistivity is found in the Ta-only sample with mixed tetragonal phase. By increasing the thickness of Ru layer, the tetragonal phase gradually disappears and a relatively pure hexagonal phase is obtained in the Ta(5)/Ru(30) buffered sample. Further magnetic and transport measurements revealed that the anomalous Hall conductivity nearly vanishes in the pure hexagonal sample, while an abnormal asymmetric hump structure emerges in the low field region. The extracted additional Hall term is robust in a large temperature range and presents a sign reversal above 200K. The abnormal Hall properties are proposed to be closely related with the frustrated spin structure of D019 Mn3Ga.