Mössbauer-effect study of spin-density waves in chromium and its alloys

Abstract

The influence of substitutional impurity atoms of Sn, Fe, V and Mn on spin-density waves (SDW) of chromium is studied by means of 119Sn-site Mössbauer-effect spectroscopy at room temperature. It is shown that the shape of 119Sn-site Mössbauer spectra, which from theoretical study of Le Caer and Dubiel is known to be sensitive to various parameters of SDW, does not depend on the Sn content in the Cr matrix; hence, Sn are ideal probe nuclei to study the issue. Fe and V atoms, however, change the corresponding Mössbauer spectra in such a way that the average hyperfine field decreases with increasing contents of these two impurities. This can be interpreted in terms of a quenching effect on SDW. Mn atoms, on the other hand, cause a steep increase of the average hyperfine field, i.e., they increase the average amplitude of SDW and simultaneously they change the shape of the Mössbauer spectra towards a six-line pattern which is an indication of a transition from incommensurate to commensurate character of SDW. The shape of the Mössbauer spectra of chromium turns out to depend substantially on the size of grains, which can be taken as evidence that grain boundaries play a key role in modifying SDW and thereby the shape of Mössbauer spectra. It is shown that they can be analyzed in terms of higher-order harmonics. Finally, it is shown that the Mössbauer spectra are sensitive to strain.