OPTICAL SPECTROSCOPY INVESTIGATIONS OF HALF METALLIC FERROMAGNETIC HEUSLER ALLOY THIN-FILMS - PTMNSB, NIMNSB, AND CUMNSB

We have studied the optical properties of cosputtered XMnSb (X=Cu,Ni,P t) thin films using light transmission, reflection, and spectroscopic ellipsometry. We observed a feature in the transmission spectra sugges tive of a band gap of energy similar to 1.5-1.7 eV for PtMnSb, similar to 1.1 eV for NiMnSb and similar to 0.8 eV for CuMnSb. This behavior is consistent with predictions of the half metallic ferromagnetic stat e in PtMnSb and NiMnSb. The values for PtMnSb and NiMnSb are larger th an the ones previously reported by other authors on bulk polished samp les. We interpret this discrepancy as due to surface contamination of the bulk samples or nonstoichiometry in our films. (C) 1997 American I nstitute of Physics.