Magnetic tunnel junctions with an equiatomic quaternary CoFeMnSi Heusler alloy electrode

Tunnel magnetoresistance (TMR) in MgO-based magnetic tunnel junctions (MTJs) with equiatomic quaternary CoFeMnSi Heusler and CoFe alloy electrodes is studied. The epitaxial MTJ stacking structures were prepared using ultrahigh-vacuum magnetron sputtering, where the CoFeMnSi electrode has a full B2 and partial L2(1) ordering crystal structure. Maximum TMR ratios of 101% and 521% were observed at room temperature and 10 K, respectively, for the MTJs. The large bias voltage dependence of the TMR ratio was also observed at low temperature (LT), as similarly observed in Co2MnSi Heusler alloy-based MTJs in the past. The physical origins of this relatively large TMR ratio at LT were discussed in terms of the half-metallicity of CoFeMnSi. Published by AIP Publishing.