Abstract
We have successfully grown both L21 polycrystalline Co2CrAl and epitaxial L21-structured Co2FeAl films onto GaAs(001) substrates under an optimized condition. Both structural and magnetic analyses reveal the detailed growth mechanism of the alloys, and suggest that the Co2CrAl film contains atomically disordered phases, which decreases the magnetic moment per f.u., while the Co2FeAl film satisfies the generalized Slater–Pauling behavior. By using these films, magnetic tunnel junctions (MTJs) have been fabricated, showing 2% tunnel magnetoresistance (TMR) for the Co2CrAl MTJ at 5K and 9% for the Co2FeAl MTJ at room temperature (RT). Even though the TMR ratio still needs to be improved for future device applications, these results explicitly include that the Co2(Cr,Fe)Al full Heusler alloy is a promising compound to achieve half-metallicity at RT by controlling both disorder and surface structures in the atomic level by manipulating the Fe concentration.
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