Sn119Mössbauer-effect studies in Heusler alloysPd1+zMnSb1−xSnx—Compositional and heat-treatment effects

Abstract

M\ossbauer-effect experiments on samples of ${\mathrm{Pd}}_{2}$Mn${\mathrm{Sb}}_{0.99}$${\mathrm{Sn}}_{0.01}$ performed systematically as a function of heat treatment have revealed the existence of three $^{119}\mathrm{Sn}$ magnetic field sites characterized by high-, intermediate-, and low-field values. A high-field site of 210\ifmmode\pm\else\textpm\fi{}5 kOe is identified with Sn replacing Sb in the ordered $L{2}_{1}$ structure of ${\mathrm{Pd}}_{2}$MnSb. An intermediate-field site of about 100 kOe is identified with a defect Sn environment which probably consists of 4 Pd vacancies in the near-neighbor coordination of the regular high-field site. The identification of the intermediate-field site is suggested by a set of measurements performed as a function of Pd composition $z$ in ${\mathrm{Pd}}_{1+x}\mathrm{Mn}{\mathrm{Sb}}_{0.995}{\mathrm{Sn}}_{0.005}$ samples, which revealed the Sn field in the $C{1}_{b}$ structure of PdMnSb to be 100 kOe. Finally, a low-field site (\ensuremath{\sim}0 kOe) is observed on prolonged annealing ${\mathrm{Pd}}_{2}$Mn${\mathrm{Sb}}_{0.99}$${\mathrm{Sn}}_{0.01}$ samples. This site is shown to be formed irreversibly due to the presence of oxygen contamination and represents a defect Sn site whose structure is less certain. The $^{119}\mathrm{Sn}$ field results in PdMnSb and ${\mathrm{Pd}}_{2}$MnSb hosts are compared with estimates of these fields based on the Jena-Geldart model.