Mössbauer-Effect Determination of the Crystalline Electric Field Parameters in Thulium Metal

Abstract

By measuring the temperature dependence of the nuclear quadrupole splitting of the 8.42-keV Mossbauer transition in the paramagnetic state of thulium metal, a determination of the crystalline electric field (CEF) parameters of elemental thulium has been obtained. The nuclear quadrupole interaction was studied within the temperature range 59 to 156°K. It was found that a zero-order calculation was sufficient to fit theory to experiment, and that in particular only C 2°, pi, and p 2 ' (where the p's account for shielding constants and the temperature-independent contributions to the electric field graident at the nucleus) were needed to fit the theory to the data, The remaining CEF parameters, C 4°, C 6°, and C 6 6 , were constrained to equal zero in the fitting routine. The over-all splitting of the Z H G ground multiplet was found to be 76.1 cm" 1 . This study also includes a determination of electronic shielding factors for thulium. The atomic Sternheimer factor RQ was found to be 0.16; and the constant <r 2 , which represents the shielding of the 4/shell from the CEF by the closed outer shells, was found to be 0.34. The latter quantity was obtained under the assumption that screening of the Tm +3 ions by the conduction electrons can be neglected. The direct lattice contribution and the conduction-electron contribution to the net electric field gradient at the Tm nucleus were found to be positive and of the same order of magnitude.

Study of combined magnetic and electric hyperfine interactions for cadmium in Dysprosium by time differential perturbed angular correlations

“…In other cases, however, the shielding effect seems to be quite small compared to the antishielding effect. For the pure metals Tm [28], La [29], Cd [20] and the impurity Cd in Indium [20] the same sign was deduced for the lattice EFG and the conduction electron EFG. In these cases the conduction electron contribution is only 1.1 to 1.8 times larger than the lattice contribution.…”

A study of crystalline electric fields in some thulium aluminum compounds

“…In comparing this data with previous data it was noted that the crystal-field splitting is much larger than previously found for rareearth metallic compounds (12,13), but still smaller than those of rareearth salts (7). Some covalency effects may be present since the fitted asymmetry parameter does not agree with that calculated using the point-ion model.…”

Study of crystalline electric fields in some thulium aluminum compounds

“…As can be seen in Figure 1, the ME spectrum consists of five indivi- This asymmetric pattern has been noted in previous studies (7,12,13,17), but it was still possible to fit the pattern with two Lorentzian lines. However, the Tm 3 Al 2 spectra could not be fit this way since the observed asymmetry is much more pronounced.…”

“…However, his results suggest little shielding or even anti-· shielding for the fourth-and sixth-order terms, in agreement with the ideas of Burns. However, semi-empirical fits with the data for various rare earth materials (7,(11)(12)(13)(14)(15) indicate some agreement with the secondorder shielding term. · Unfortunately, these experiments are not conclusive in regards to higher-order terms.…”