Structural, magnetic, and transport properties of polycrystalline Mn₃Ga_0.8Ge_0.2 alloy

DO₁₉-ordered Mn₃Ga gained much attention recently due to their potential application in spintronic devices. However, there still remain several challenges to overcome before their practical application. We have studied the structural, magnetic, and transport properties of polycrystalline Mn₃Ga_0.8Ge_0.2. It was found that Ge-doped Mn₃Ga ingot undergoes a spin reorientation transition from a coplanar antiferromagnetic to a noncoplanar configuration of Mn moments at around 200 K, accompanied by the competition among magnetocrystalline anisotropy, ferromagnetic interaction, and antiferromagnetic coupling. Compared with other reports on polycrystalline Mn₃Ga, the Mn₃Ga_0.8Ge_0.2 alloy in our work has a higher spin reorientation transition temperature, which is related to the lattice distortion caused by Ge doping. The anomalous Hall effect can be observed from 10 to 350 K and the Hall resistivity at room temperature is 0.641 μΩ cm. An apparent topological Hall effect (THE) was observed simultaneously in the hexagonal non-collinear polycrystalline Mn₃Ga_0.8Ge_0.2 ingots below 200 K. The origin of the present THE is attributed to the non-collinear triangular magnetic configuration with slight distortion. The maximum value of topological Hall resistivity can reach a value of about 0.242 μΩ cm at 120 K. Our work provides an approach for topological spintronics applications using Mn₃X-based alloys.