NiN Epitaxial Thin Films*

Antiferromagnets with emergent anomalous Hall effect establish new directions for spintronic applications, with faster switching dynamics compared to ferromagnetic counterparts. The noncollinear antiferromagnet Mn₃NiN, providing a unique combination of metallic resistivity and anomalous Hall effect via Berry phase mechanisms, is a promising candidate. We have grown high-quality epitaxial Mn₃NiN thin films on (001) LSAT substrates via reactive magnetron sputtering. Below the 240 K Neel temperature, these films show an anomalous hall effect significantly larger than conventional ferromagnets, understood through their non-vanishing Berry curvature arising from the Γ^4g-type noncollinear antiferromagnetic spin arrangement. In addition, a small tetragonality induces a net magnetic moment that couples to external magnetic fields, providing control of the Γ^4g antiferromagnetic state. We demonstrated this control through a varying film tetragonality established by the N₂ fraction during reactive growth, verified by measurements of the anomalous hall resistivity. Mn₃NiN provides an ideal structural strain controlled platform for anomalous Hall effect based spintronics applications.