Tunnel magnetoresistance for magnetic tunnel junctions with Co2FeAl0.5Si0.5 full Heusler electrodes fabricated by molecular beam epitaxy system

The authors fabricated Co2FeAl0.5Si0.5 full Heusler alloy thin films by using a molecular beam epitaxy system on Cr buffered MgO single crystal substrates and investigated their structural and magnetic properties. It was revealed that Co2FeAl0.5Si0.5 films formed ordered L2(1) and B2 structures after annealing above 500 degrees C and below 400 degrees C, respectively. Then magnetic tunnel junctions with these electrodes and Al-oxide or MgO barriers were also fabricated, and the bias voltage dependence of tunnel magnetoresistance ratio was investigated. It was found that the tunnel magnetoresistance ratio of the junction with Al-oxide barrier has a larger asymmetric bias voltage dependence compared with that with MgO barrier, and the negative tunnel magnetoresistance ratio at high negative bias voltage is observed for both junctions. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3072448]