Mn₂CrGa-based Heusler alloys with low net moment and high spin polarization

Mn₂CrGa-based Heusler compounds combining small magnetization with high spin polarization, fabricated by Fe and Pt substitution for Cr, are investigated experimentally and discussed in terms of sublattice site occupancies. X-ray diffraction and electron diffraction indicate that the parent alloy and Mn₂Cr_0.6Fe_0.4Ga are normal cubic Heusler alloys with substantial chemical disorder, whereas Mn₂Cr_0.6Pt_0.4Ga crystallizes in the tetragonal D0₂₂ structure. Magnetization measurements indicate that the spin structure of the parent alloy is essentially ferrimagnetic, but alloying with Fe or Pt reduces the net magnetization per formula unit from 0.40 μ _B in the parent alloy to nearly zero in the Fe case. The Curie temperature, the magnetoresistance, and the Andreev-reflection transport-spin polarization are less affected by the substitutions, the last changing from 65% in Mn₂CrGa to 60% and 61% in the Fe- and Pt-substituted alloys, respectively. The properties of these alloys are favorable for spintronics applications.