Planar Hall effect caused by the memory of antiferromagnetic domain walls in Mn3Ge

In Mn3X (X = Sn, Ge) antiferromagnets, domain walls are thick and remarkably complex because of the non-collinear arrangement of spins in each domain. A planar Hall effect (PHE), an electric field perpendicular to the applied current but parallel to the applied magnetic field, was recently observed inside the hysteresis loop of Mn3Sn. The sign of the PHE displayed a memory tuned by the prior orientation of the magnetic field and its history. We present a study of the PHE in Mn3Ge extended from room temperature down to 2 K and show that this memory effect can be manipulated by either a magnetic field or thermal cycling. We show that the memory can be wiped out if the prior magnetic field exceeds 0.8 T or when the temperature exceeds T N. We also find a detectable difference between the amplitude of the PHE with zero-field and field thermal cycling. The ratio between the PHE and the anomalous Hall effect decreases slightly as temperature is increased from 2 K to T N and tracks the temperature dependence of magnetization. This erasable memory effect may be used for data storage.