Transport properties of Heusler compounds Fe3-xMnxSi (x = 1.6, 1.7 and 1.8) under magnetic fields

Measurements of the electrical resistivity, magnetoresistance (MR), and Hall effects are performed to investigate the transport properties of Fe3-xMnxSi (x = 1.6, 1.7, and 1.8) under magnetic fields. It is known that Fe2MnSi exhibits a ferromagnetic transition at TC and an antiferromagnetic transition at a lower temperature (TA) to the phase referred to as the AF phase. A recent study on Fe1.3Mn1.7Si found another antiferromagnetic transition at a temperature below TA, defined as TA2, to a phase referred to as the AF2 phase. In this study, in MR measurements for x = 1.7 and 1.8, the change in MR with magnetic field is found to transition from positive to negative at certain magnetic fields. Comparing these results with those of magnetization measurements, these points correspond to the AF2-AF transitions. The results also indicate that these transitions occur at a higher field for x = 1.8 than for x = 1.7. The Hall effect measurements show the anomalous Hall effect for x = 1.6 and 1.7 in the temperature region where spontaneous magnetization is present, but not for x = 1.8, for which the ferromagnetic state appears to be absent. These results are consistent with the magnetization measurements.