Anomalous giant magnetoresistance in Heusler-type alloys Fe2+xV1-xGa

Electrical resistance, magnetoresistance and magnetization were measured for Heusler-type alloys, Fe2+xV1-xGa. An anomalous giant magnetoresistance (GMR) near 50% was observed for Fe2VGa which was a weak and inhomogeneous ferromagnet. For alloys with x > 0, which show clear ferromagnetism, the electrical resistance showed an anomaly below the Curie temperature. For alloys with x < 0, the temperature dependence of the resistance indicated behavior like that of a semiconductor. The energy gap was tentatively estimated to be 0.03 eV for x = -0.10. The origin of the present GMR is discussed in terms of the metal-insulator transition arising from ordering of the magnetic moment.