Growth and Characterization of Epitaxial NiMnSb/PtMnSb C1_b Heusler alloy superlattices

We have sputter deposited NiMnSb/PtMnSb Heusler alloy superlattices with bilayer periods from 9–160 Å. X-ray diffraction and cross-sectional transmission electron microscopy (TEM) measurements indicate that even for short bilayer periods, the superlattices are compositionally modulated, epitaxial, and maintain the Heusler alloy C1_b structure. Low- and high-angle diffraction profiles are in agreement with simulations of the superlattice peaks. TEM images reveal defects, including stacking faults, which help relieve lattice mismatch strain. Energy minimization calculations of the stacking fault density are within a factor of 3 of the density observed by TEM. The saturation magnetization of the superlattices is close to bulk PtMnSb and NiMnSb, with a tendency for perpendicular magnetization at short bilayer periods.