Designing compensated magnetic states in tetragonal Mn3Ge-based alloys

Magnetic compensated state attracted much interests due to the observed large exchange bias and large coercivity, and its potential applications in the antiferromagnetic spintronics with merit of no stray field. In this work, by ab initio calculations with KKR-CPA for the treatment of random substitution, we obtain the complete compensated states in the Ni (Pd, Pt) doped Mn3Ge-based D022-type tetragonal Heusler alloys. We find the total moment change is asymmetric across the compensation point (at ~ x = 0.3) in Mn3-xYxGe (Y = Ni, Pd, Pt), which is highly conforming to that experimentally observed in Mn3Ga. In addition, an uncommon discontinuous jump is observed across the critical zero-moment point, indicating that some non-trivial properties can emerge at this point. Further electronic analysis for the three compensation compositions reveals large spin polarizations, together with the high Curie temperature of the host Mn3Ge, making them promising candidates for spin transfer torque applications.