Superposition Model Analysis of the Spin Hamiltonian Parameters of Two Gd³⁺ Doped Thorium Dichalcogenides

Abstract

The spin Hamiltonian parameters of Gd 3+ in a single crystal of Thorium disulfide (TI1S2) are analysed by means of the superposition model, in its most general form of a two exponents power law. In fact, the approximated one exponent power law is not suitable for this compound, where the ion-ligand distances show a quite large spread. The results of the analysis are then applied to the case of Gd 3+ doped Thorium oxysulfide (ThOS), where the fitting of the experimental data is possible only assuming some distortion of the ligand cage.

The Refined Structure of ThS2 and the Implications on the Superposition Model Analysis of ThS2: Gd3+ Spin Hamiltonian Parameters

“…The coordination factors vary appreciably with respect to the values quoted in [1], confirming that an accurate determination of the positional param eters is needed, particularly in low symmetry systems.…”

“…metal-ligand distances and the second degree coordination fac tors, relative to the crystal field reference frame (see Figure 1). We have maintained the same numbering of the ligands as in [1], However it does no more corre spond to the increasing order, as the S4,4< and S5 ligand distances are now inverted.…”

“…The set of parameters values given in [1] was: A = 3, B = -2, R0=3.00A , tA = 7.7, tB= 11.35, b2(Ro) = -1161 • 10-4 cm-1.…”

“…It has been shown in [1] that without loss of generality the coefficients Ä and B can be fixed at the quoted values, already proposed by Newman and Urban [7], Moreover, a suitable value of the reference dis tance R0 can be chosen to determine the values of tA, rB and b2(R0) from the fitting of the experi mental data. Conversely, for a given value of tA, the corresponding values of tB, R0 and b2{RQ) can be found.…”

“…In a preceding paper [1] the superposition model (SPM) analysis was succesfully applied to the sec ond degree crystal field parameters of substitutional Gd3+ in ThS2 and ThOS matrices.…”