Mössbauer Effect in Ni-Pd Alloys
- 1 October 1972
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 6 (7), 2796-2808
- https://doi.org/10.1103/physrevb.6.2796
Abstract
We have obtained nuclear -resonance (NGR) absorption spectra with the 67.4-keV transition from in Ni-Pd alloy absorbers throughout the concentration range 0-99.5 at.% Pd. The source contained the parent isotope , produced by the reaction , in a nonmagnetic -14 at.% V foil. Both source and absorber were immersed in liquid helium. Values of the absorber recoilless fraction, energy shift, and absolute value of the hyperfine (hf) field were obtained for each concentration studied. In the ferromagnetic region 0-98 at.% Pd, the spectra showed a partly resolved magnetic hyperfine splitting with a distribution of magnetic hyperfine fields. The average hyperfine field is negative in pure Ni (-76 kOe), changes sign near 50 at.% Pd, and rises to a large positive value (+173 kOe) at 90 at.% Pd. Qualitative agreement with these results is obtained with a model based on the assumption that in Ni-Pd has the same contributions from core polarization and bulk conduction-electron polarization as in other Ni-based alloys, plus a large positive contribution from Pd atoms on neighboring lattice sites. From measurements with an external magnetic field in alloys containing 50-99.5 at.% Pd, we find that the calculated average hyperfine fields are in agreement with the values expected for no distribution of fields. The distribution width of hyperfine fields is kOe in the mid-concentration range. In an alloy containing 0.5 at.% Ni, the most dilute alloy studied, the moment was obtained. From a temperature-dependence study of the second-order Doppler shift, we have deduced the relative isomer shift between in Pd and in Ni to be μ/sec.
Keywords
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