Mössbauer Effect Studies of Nuclear Hyperfine Structure inTm169inFe2Tm

The nuclear hyperfine structure of the 8.4-keV transition in ${\mathrm{Tm}}^{169}$ in ${\mathrm{Fe}}_2$Tm has been studied as a function of temperature from 4 to 400°K using the Mössbauer effect. The main source of the nuclear hyperfine interaction is the Tm $4f$ electron shell which is polarized through the exchange interaction with the iron atoms, which are themselves ferromagnetically coupled. A theoretical analysis based on the assumption that the thulium ion ground-state energy levels are determined only by this exchange interaction is successful in explaining the observed temperature variation of the magnetic and electric nuclear interactions. The magnetic hyperfine interaction in the nuclear ground state is 1.05±0.05×${10}^{-5\mathrm{}}$ eV at 4°K. The nuclear quadrupole moment of the 8.4-keV state has been estimated to be -1.3 b, the ratio $\frac{{\mu }_e}{{\mu }_g}$ of the nuclear magnetic moments is -2.17±0.10, the magnetic moment of the Tm ion in Tm metal at 4°K is 6.4±0.3 ${\mathrm{\mu }}_{\mathit{B}}$, and the value $〈r^{-3\mathrm{}}〉$ for the $4f$ electrons has been measured as 12.5±0.7 au. These results are compared with the theoretical values and other experimental results.