Effect of Cr substitution for Fe on the spin polarization of Co2CrxFe1-xSi Heusler alloys

We have investigated the effect of Cr substitution for Fe on the spin polarization, P, of Co2CrxFe1-xSi alloys using the point contact Andreev reflection method. A steep increase from P=0.57 to P=0.64 occurs by a small substitution of Cr for Fe of x=0.02, thereafter P values are constant for higher Cr concentrations up to x=0.4. The increase in spin polarization can be attributed to both the improved L2(1) ordering found experimentally as well as the half-metallicity predicted by ab initio calculations in the composition range of 0 <= x <= 0.5. We propose the composition range of 0.02 <= x <= 0.1 is the most promising for ferromagnetic electrodes of magnetic tunneling junctions to achieve high tunneling magnetoresistance. (C) 2007 American Institute of Physics.