Isotropic Negative Magnetoresistance in Mn₅Si₃/MnSi Films

Altermagnets have garnered significant attention for combining antiferromagnetic traits, such as vanishing net magnetization and ultrafast spin dynamics, with ferromagnetic properties, making them attractive for spintronic applications. One candidate material for this emerging magnetic category is Mn₅Si₃^1,2. In this study, we report the observation of an isotropic negative magnetoresistance (MR), up to 17% at 40 K from a series of films composed of both Mn₅Si₃ and MnSi. The observed large MR is mostly isotropic in longitudinal, transverse, and perpendicular measurement geometries, characteristic of giant magnetoresistance. The films were deposited onto sapphire substrates. X-ray diffraction analysis reveals a two-phase structure with both Mn₅Si₃ and MnSi, of which the relative ratio can be tuned by changing the growth conditions. Both saturation magnetization and MR signal are found to vary as the relative ratio of Mn₅Si₃ and MnSi changes. Interestingly, a 9% MR at 40 K persists while the saturation magnetization is reduced to 15 emu/cm³. Moreover, the MR signal is temperature-dependent, peaking at approximately 40 K for this series of films. These results demonstrate a promising MnSi_x system with sizable MR, for explorations of spintronic devices that leverage the vanishing stray field.

[1] L. Šmejkal., et al., Phys. Rev. X 12, 040501 (2022)

[2] L. Šmejkal., et al., Phys. Rev. X 12, 011028 (2022)