Abstract
The hyperfine magnetic field (HMF) distribution in bcc Fe-Ni alloys was calculated with a model of linear response of the HMF to magnetic moments in the alloy. With the use of empirical parameters, the model largely accounts for the HMF distribution at low temperatures. As shown by experiments with Si solutes in Fe-Ni, the anomalously strong temperature dependence of the HMF in Fe-Ni is not due to the temperature dependence of the HMF response parameters. By analyzing the shape of the HMF distribution, we find that this anomalous temperature dependence results from a large thermal sensitivity of the magnetic moments at those Fe atoms with more Ni atoms as nearest neighbors. This correlated with a strong temperature dependence of the recoil-free fraction and the second-order Doppler shift in Fe-Ni. We suggest that the large mean-square thermal displacement of Fe atoms in Fe-Ni is the cause of the anomalously strong temperature dependence, and we offer two explanations for this effect. Additionally, we have found evidence for a pseudodipolar interaction in Fe-Ni, and we also discuss the problems of parametrizing the HMF solely in terms of the number of nearest neighbors of the atom.
- Received 29 April 1985
DOI:https://doi.org/10.1103/PhysRevB.34.4480
©1986 American Physical Society