High Magnetic Field Effect and Composition Dependence of Magnetooptical Kerr Rotation for the Heusler Compound PtMnSb

The magnetooptical Kerr rotation angle ¿K for the polished surfaces of bulk PtMnSb samples was measured at 632.8 nm in strong magnetic fields. The saturation value of ¿K for the stoichiometric sample was 1.42° in the as-polished state, and was improved to 1.75° by annealing at temperatures higher than 400°C. It is suggested that the improvement in ¿K is caused by the decrease in the imaginary part of the diagonal elements of the dielectric constant tensor. It was also found that ¿K depends strongly on the composition in the Pt-Mn-Sb ternary system, and takes a maximum at the stoichiometric composition.