Enhancement of giant magnetoresistance by L21 ordering in Co2Fe(Ge0.5Ga0.5) Heusler alloy current-perpendicular-to-plane pseudo spin valves

We report large magnetoresistance (MR) output in fully epitaxial Co2Fe(Ge0.5Ga0.5)/Ag/Co2Fe(Ge0.5Ga0.5) current-perpendicular-to-plane pseudo spin valves. The resistance-area product change (Delta RA) of 12 m Omega mu m(2) at room temperature (RT), equivalent to MR ratio of 57%, and Delta RA = 33 m Omega mu m(2) at 10 K, equivalent to MR ratio of 183%, were obtained by using L2(1)-ordered Co2Fe(Ge0.5Ga0.5) ferromagnetic electrodes. The bulk spin scattering asymmetry (beta) were estimated to be similar to 0.83 at RT and similar to 0.93 at 10 K for the L2(1)-ordered Co2Fe(Ge0.5Ga0.5) films by the Valet-Fert model, indicating that the L2(1)-ordered Co2FeGe0.5Ga0.5 Heusler alloy is virtually half-metal at 10 K, but its half-metallicity is degraded at RT. (C) 2013 AIP Publishing LLC.