Anisotropic magnetoresistance and planar Hall effect in single crystals of metallic topological ferroelectric Ni₂P

Based on crystallographic studies and band structure calculations, Ni₂P was suggested to be a real-space topological ferroelectric, exhibiting spin-dependent band splitting and band crossing near its Fermi level [1]. We present detailed angle-resolved magnetotransport measurements of Ni₂P single crystals grown by two different ways. By sweeping the magnetic field (B) in longitudinal, transverse, and in-plane directions relative to the current (J) directions, we probe both the magnetoresistance (MR) and the Hall effect. When B is nearly parallel to J, we observe clear deviations in MR scaling with the projections of magnetic fields normal to the sample plane. Additionally, for in-plane fields, we detect planar Hall effect, which likely originates from the anisotropy of the Fermi surface since the system is non-magnetic. Furthermore, we investigate the effect of non-magnetic disorder introduced by low-temperature electron irradiation and propose possible explanations for the observed violation of Matthiessen's rule and the suppression of MR.

[1] X. K. Wei et al., Discovery of Real-Space Topological Ferroelectricity in Metallic Transition Metal Phosphides, Adv. Mater. 32, 46 (2020).