Tuning crystal orientation and chiral spin order in Mn₃Ge by annealing process and ion implantation

The non-collinear antiferromagnetic Weyl semimetal Mn3X (X = Ga, Ge, Sn) system has attracted a lot of attentions owing to its robust anomalous Hall effect (AHE), large spin Hall angle and small net magnetization at room temperature. The high spin-charge interconversion efficiency makes it a super candidate in topological antiferromagnetic spintronic devices, which could facilitate ultra-fast operation of high-density devices with low energy consumption. In this work, we have realized to obtain different chiral spin structures in Heusler alloy Mn3Ge thin films, which originate from different crystalline orientations. The high-quality (0002)- and (20 (2) over bar0)-oriented single phase hexagonal Mn3Ge films are achieved by controllable growth, annealing process and ion implantation. The various magnetic properties and AHE behaviors are observed along a and c crystal axes, equivalent to magnetic field in and out of the inverse triangular spin plane. The observation demonstrates the manipulation of crystal structure accompanied with chiral spin order in a non-collinear antiferromagnetic Mn3Ge film, which is induced by energy conversion and defect introduction. The in situ thermal treatment induces crystal phase rotation up to 90 degrees and robust AHE modulation, which is significantly important and highly desirable for flexible spin memory device applications.