Internal magnetic field inα−FeSO4

Abstract

From many-electron cluster wave functions of $\ensuremath{\alpha}\ensuremath{-}\mathrm{FeS}{\mathrm{O}}_{4}$, which where obtained from semiempirical calculations with a ${[\mathrm{F}\mathrm{e}{(\mathrm{S}{\mathrm{O}}_{4})}_{6}]}^{\ensuremath{-}10}$ cluster in our study, we derive various contributions to the internal magnetic field (${H}^{\mathrm{int}}$) at 4.2 K. Its main contribution with - 544 kG comes from the core polarization of Fe $\mathrm{Fe} \mathrm{ns}$ atomic orbitals. The relatively small charge transfer of about 0.13 electron charges into the Fe $\mathrm{Fe} 4s$ atomic orbital contributes to ${H}^{\mathrm{int}}$ with more than + 60 kG due to the spin polarization of Fe $\mathrm{Fe} 4s$ electrons. The orbital and spin dipolar terms are of the order + 150 and + 100 kG, respectively; their values are sensitive upon the choice of $〈{r}^{\ensuremath{-}3}〉$. The supertransferred hyperfine field is negative since $\ensuremath{\alpha}\ensuremath{-}\mathrm{FeS}{\mathrm{O}}_{4}$ is antiferromagnetic at low temperatures; its absolute value (15 kG) is relatively small, because we have only two Fe-O-Fe chains per cluster. The deviation of ${H}^{\mathrm{int}}$ from the spin direction ($z$) by about 12\ifmmode^\circ\else\textdegree\fi{} is due to the dipolar field. Our calculated values are comparable with the experimental result of ${H}^{\mathrm{int}}=212\ifmmode\pm\else\textpm\fi{}3$ kG from Wehner's work.