Crossover of magnetoresistance in the zero-gap half-metallic Heusler alloy Fe 2 CoSi

This work reports on band structure and magneto-transport investigations of the inverse Heusler compound Fe 2 CoSi. First-principles calculations show that Fe 2 CoSi has a very peculiar band structure with a conducting property of the majority spin channel and a nearly zero bandgap in the minority spin channel. The prepared Fe 2 CoSi sample possesses a highly ordered inverse Heusler structure with a magnetic moment of at 5 K and a high Curie temperature of 1038 K. With increasing temperature, a crossover from positive to negative magnetoresistance (MR) is observed. Combining this with the Hall effect measurements, we suggest that the intriguing crossover of the MR can be ascribed to the dominant spin carriers that change from the gapless minority spin channel to the majority spin channel at the Fermi level.