Tunneling Magnetoresistance in MnRuGa based Magnetic Tunnel Junctions

Some intermetallic Heusler compounds display high spin polarization and low magnetic moment. Thin-film samples can possess huge uniaxial anisotropy fields, exceeding tens of teslas. This, combined with their tuneable properties, make these materials very attractive for THz based spin-transfer-torque oscillators. Recently new material from this family was discovered - MnRuGa (MRG) - the first experimentally achieved fully-compensated half-metallic ferrimagnet. Here we show that MRG can be integrated in perpendicular anisotropy magnetic tunnel junctions stacks. Tunneling magnetoresistance (TMR) ratios up to 40% are observed. We also demonstrate that the TMR exists even when the net magnetization of MRG is strictly zero, implying that, at compensation, MRG exhibits a sizable spin polarization. The role of different diffusion barrier layers between MRG and the tunneling barrier as well as annealing temperature was investigated.

This work is supported by the Helmholtz Young Investigator Initiative Grant No. VH-N6-1048.