Hyperfine field distributions in disordered Mn2CoSn and Mn2NiSn Heusler alloys

Abstract

Heusler alloys, Mn 2 CoSn and Mn 2 NiSn, were prepared and characterized by X-ray studies. Mössbauer studies using Sn-119 were carried out to investigate the hyperfine fields present at the Sn site in these alloys. The hyperfine field distribution in these alloys as well as X-ray studies point to the chemical disorder present in both alloys. Coexistence of a paramagnetic portion along with the magnetic hyperfine part was observed in Mn 2 CoSn even at low temperatures, while this was not found in Mn 2 NiSn spectra. Hyperfine fields at Sn site were calculated using Blandin and Campbell model and compared with the experimental results.

Electronic, magnetic, and structural properties of the ferrimagnet Mn2CoSn

“…Experiments on Mn 2 CoSn were previously reported by different groups [24][25][26][27]. According to Ref.…”

Atomic order and transferred hyperfine field in Co2TiSn reexamined by tin-119 Mössbauer spectroscopy

“…The observed fields, which are presumably positive, [4,10,11] decrease as expected with increasing temperature. The actual fields observed for Co 2 TiSn are much smaller than those observed [10][11][12] in the manganese containing Heusler alloys in which the manganese atoms carry a large magnetic moment. In Co 2 YSn, where Y is Sc, Ti, V, Zr, or Nb, [4,5] the transferred hyperfine field on the tin atoms results from a polarisation of the conduction electrons by the cobalt magnetic moments.…”

Evidence of Clustering in Heusler like Ferromagnetic Alloys

“…Thus the coexistence of paramagnetic peak in Mn 2 CoSn can be understood to be due to clustering of Mn atoms around some of the Sn atoms. Another such disordered alloy, Mn 2 NiSn was prepared and studied in an identical manner [12]. Interestingly, this alloy behaved like an ordinary ferromagnet and did not show the presence of any paramagnetic peak co-existing with the magnetic hyperfine spectrum, indicating that the disorder in this case was confined to a nearly equal distribution of Ni and Mn between the A[C] and B sites.…”

“…However, it is single phased. Sn-119 Mössbauer spectra were recorded over a range of 50 K to 670 K. In all these spectra co-existence of a magnetic hyperfine component with a central paramagnetic peak was observed at all temperatures [12]. The spectra were fitted using the Window method with widths constrained to those of natural Sn.…”