Room-Temperature Perpendicular Magnetization and Anomalous Hall Effect in Polycrystalline Antiferromagnetic γ-FeMn Films

Noncollinear antiferromagnets can exhibit intriguing topological phenomena, such as orbital magnetism and anomalous Hall (AH) effects [1-2]. However, topological antiferromagnets films require growth or annealing at high temperatures [1-2], posing difficulty for device manufacturing. Here, we show net out-of-plane magnetism and AH response at room temperature in sputter-grown polycrystalline FCC FeMn without any high-temperature growth or annealing. Since FeMn is a widely used antiferromagnets for exchange-biasing, its potential as a topological material is attractive for practical applications.

Theoretical works [3-4] predict topological magnetism and transport in FCC antiferromagnets with scalar spin chirality from the (111) orientation and uniaxial strain. The key to our (111) oriented FCC FeMn is an ultrathin Cu seed layer. We observe perpendicular magnetization superficially reminiscent of topological antiferromagnets with a uniaxial strain present in the FCC FeMn ~1.4% [5]. Our findings indicate that commonplace 𝞬-FeMn alloys, long used for exchange biasing since the 1970s, can be transformed into practical alternatives to topological antiferromagnets in spintronic devices.

[1] Taylor, J. M., et al., Phys Rev B, Vol. 101, pgs. 094404, (2020)

[2] Nakatsuji, S., et al., Nat, Vol. 527, pgs. 212-215, (2015).

[3] Hanke, J. P., et al., Sci. Rep, Vol. 7, pg. 41078, (2017)

[4] Kubler, J., et al., Jour. of Phys F: Met. Phys, Vol. 18, (1988)

[5] Cankurtaran, M., et al, Phys Rev B, Vol. 47, pgs. 3161-3170, (1993).