Structural defects and magnetic properties in the ordered compound CoGa

The magnetic susceptibility of the β-phase CoGa has been correlated with the defect structure of this phase. If only vacancies on the Co-sublattice (i.e. T-atom sublattice) and Co-atoms on the Ga-sublattice (i.e. transition antistructure atoms or TAS-atoms) are considered, their concentrations can be evaluated by density measurements combined with lattice constant determination. The susceptibility consists of a Curie-Weiss term which can be explained by magnetic moments located at TAS-atoms. The effective local magnetic moment per TAS-atom is found to be (5.02±0.06)μ_B. This value is independent of alloy composition and of heat treatment and is valid in the whole composition range for alloys quenched from 900°C as well as for those annealed after quenching or cooled slowly from high temperatures. With annealing out of quenched-in TAS-atoms the susceptibility decreases as predicted by this model.