First-principles study of the carrier doping effect on all-Heusler GMR junctions

In this work, we investigate interfacial magnetic couplings and spin-dependent transport property in all-Heusler based CPP-GMR junctions with a semimetallic Fe₂VAl spacer on the basis of first-principles calculations. A half-metallic ferrimagnet Mn₂VAl is used for a spin injector and is thought to be highly promising for spintronics devices at room temperature because the expected current to flip the spin would be rather low. It is found from our calculations that, in MnMn-VAl termination, the interfacial Mn atoms are antiferromagnetically coupled with V atoms of Fe₂VAl. In addition, half-metallic states are also preserved in the interfacial reigion. The transport property is governed by an electron pocket in the band structure, originating from the V d states. The carrier doping effect from band matching leads to a new function in CPP-GMR junctions. When carriers are introduced in the spacer by a gate voltage, magnetoresistance might be changed significantly. Moreover, from comparison with a spin injector with another half-metallic Heusler alloy Co₂MnSi, the chemical trend in this type of CPP-GMR junctions is discussed.