Equilibrium Chemical Disorder at the Surface of a Single-Crystal C1b NiMnSb Half-Heusler Alloy: Implications for Spintronics

The structural and chemical short-range order in a NiMnSb Heusler-type single crystal is measured using extended X-ray absorption fine structure (EXAFS). A parameterized nonlinear least squares fitting of the Ni and Mn K and Sb L-I EXAFS using theoretical EXAFS data generated via a multiple scattering approximation are compared with results from neutron diffraction data. EXAFS results are consistent with a C1(b) structure with a quantifiable Ni-Mn chemical short-range disorder in the surface region of the Czochralski-grown single crystal that explains the often-reported low spin polarization.