A neutron diffraction and magnetization study of Heusler alloys containing Co and Zr,Hf, V or Nb

Neutron diffraction, X-ray diffraction and saturation magnetization measurements have been made on a series of ferromagnetic alloys at the composition Co₂YZ, where Y is a group IVA or VA element and Z is a group IIIB or IVB element. The alloys are mainly ordered in the Heusler L2₁ type chemical structure, but some show the presence of a small amount of additional phase, or some preferential disorder.The magnetic results form two distinct groups in which the moments are confined to the Co sites but their magnitude depends on the electron concentration determined by the Y and Z atoms. Although the magnetic moments and Curie temperatures of the alloys in the same group are similar, their lattice parameters differ according to whether Z is a group IIIB or IVB element. Such behaviour indicates that, as in other alloy series with the Heusler structure, a change in lattice parameter has little effect on the magnetic properties in comparison with the effect of a change in electron concentration.