Magnetic measurements and crystal field investigation of Tm3+ in Tm(CF3SO3)3⋅9H2O

Abstract

Single crystals of thulium trifluoromethanesulfonate (TmTFMS) were grown and the principal magnetic susceptibility χ⊥ and magnetic anisotropy Δχ(=χ∥−χ⊥) were measured in the temperature range of 300–13.5K and 300–80K, respectively. Though the value of χ⊥ is found to rapidly increase with the decrease in temperature, the value of χ∥ slowly increases with the lowering of temperature down to ∼110K, below which it slowly decreases. The hexagonal crystal structure of TmTFMS is similar to that of the isostructural series of hydrated rare earth ethylsulfates and the non-Kramers Tm3+ ion occupies a site of C3h symmetry. Our observed magnetic data were analyzed using crystal field (CF) analyses where the Hamiltonian includes the atomic free ion and (CF) (one-electron) interaction terms. The computed and measured paramagnetic susceptibilities of TmTFMS agree well in the temperature range of our study. Smooth variation of χ⊥ down to 13.5K does not indicate any structural phase transition or symmetry breaking, at least down to 13.5K. The computed nuclear quadruple splitting and electronic heat capacities give some interesting results. In order to substantiate the theoretical calculation, the Raman spectra of the compound were recorded in the wavenumber range of 10–1800cm−1. It has been found that the theoretical values of the CF Stark energies in the ground multiplet are in good agreement with the Raman data.