Sn119hyperfine fields in MnSn2

Abstract

$^{119}\mathrm{Sn}$ M\"ossbauer spectra in the antiferromagnetic compound Mn${\mathrm{Sn}}_{2}$ below ${T}_{N}\ensuremath{\sim}325$ K are in agreement with the neutron diffraction results of Corliss and Hastings. The hyperfine parameters allow us to conclude unambiguously that the transferred hyperfine fields are partially or totally anisotropic according to the magnetic tin sites. A simple field model including anisotropic and isotropic contributions accounts for the observed fields. The isotropic part, attributed to the conduction-electron polarization, oscillates and decreases with the distance to the tin site. The radial dependence is not inconsistent with an ${r}^{\ensuremath{-}3}$ variation. The anisotropic part is related to the existence of covalent bonding between Sn and the first Mn neighbors. The same model shows that the field is totally anisotropic in Fe${\mathrm{Sn}}_{2}$. These anisotropic fields are characterized by a coupling constant which is 21.9\ifmmode\pm\else\textpm\fi{}1.1 and 21.0\ifmmode\pm\else\textpm\fi{}1.3 kG${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}^{\ensuremath{-}1}$ in Mn${\mathrm{Sn}}_{2}$ and Fe${\mathrm{Sn}}_{2}$, respectively. The model, applied to the broadened spectra at 72 and 77 K, allows us to conclude that the modulated spin component, observed by neutron diffraction, is perpendicular to the antiferromagnetic axis with a relative modulation amplitude $\frac{\ensuremath{\Delta}{\ensuremath{\mu}}_{0}}{{\ensuremath{\mu}}_{0}}=0.27\ifmmode\pm\else\textpm\fi{}0.02$ at \ensuremath{\sim} 72 K. The idea that this modulation corresponds to a modulated canting angle between the two sublattices cannot be excluded.