Large negative magnetoresistance effects in Co₂Cr _0.6Fe_0.4Al

Materials, which display large changes in resistivity in response to an applied magnetic field (magnetoresistance) are currently of great interest due to their potential for applications in magnetic sensors, magnetic random access memories, and spintronics. Guided by striking features in the electronic structure of several magnetic compounds, we prepared the Heusler compound Co₂Cr_0.6Fe_0.4Al. Based on our band structure calculations, we have chosen this composition in order to obtain a half-metallic ferromagnet with a van Hove singularity in the vicinity of the Fermi energy in the majority spin channel and a gap in the minority spin channel. We find a magnetoresistive effect of 30% in a small magnetic field of 0.1T at room temperature. This demonstrates the feasibility of a cheap and simple magnetic sensor based on polycrystalline, intermetallic material.