Structural, Magnetic and Transport Properties of Co₂Cr _1-xFe_xAl Full-Heusler Alloys

The structural, magnetic and transport properties are investigated for the full-Heusler alloy Co₂(Cr_1-xFe_x) Al (CCFA) thin films deposited on thermally oxidized Si substrates at room temperature (RT). X-ray diffraction reveals that the films possess the B2 structure for x=0, decrease the atomic site ordering by substituting Fe for Cr (x=0.4∼0.6) and form the A2 structure for x=1. Both the magnetic moment and the Currie temperature of the films increase with increasing Fe content (x), although the moment for x<1 is significantly smaller than that of the calculated value for the L2₁ structure. Spin-valve type tunneling junctions with CCFA films are also fabricated by using metal masks, which demonstrate tunneling magnetoresistance (TMR) of 19% for x=0.4 at RT and 27% at 5 K despite the atomic site disorder. This is the largest TMR observation at RT with half metallic ferromagnets.