Magnetic properties, Schottky heat capacity, and the nuclear quadrupole splitting of the 8.42 keV excited state of Tm3+ on tetragonal sites in CaF2

Abstract

A crystal field (CF) calculation of the principal magnetic susceptibilities, the Schottky heat capacity, and the nuclear quadrupole splitting of the 8.42 keV excited state of the Tm3+ ion on tetragonal sites in CaF2 has been carried out in the intermediate coupling approximation. The CF parameters used were those given by Muto who obtained them from the analysis of the absorption spectra of the excited states. Our analysis gives a doublet as the ground state in the Stark pattern of the 3H6 ground manifold which is in contradiction with that stated by Muto. Though the thermal variation of the magnetic anisotropy K∥–K⊥ is similar to that of thulium ethylsulfate (TmES), the sign is positive whereas for the latter it is negative. The behavior of the square of the effective Bohr magneton number (p2eff) is similar to the case of TmES but the magnitude at very low temperatures is much larger since a doublet lies lowest. The Schottky heat capacity Cs shows a peak at 85 K similar to that of TmES but the height of the peak is much lower than that for TmES. The thermal variation of the nuclear quadrupole splitting 〈ΔEQ〉T is seen to be quite different from that of TmES but similar to the case of Tm2O3 except for the magnitudes. Experimental determination of the various quantities is suggested as a check on the CF proposed by Muto.