THEORETICAL STUDIES OF THE ZERO-FIELD SPLITTING AND g FACTOR FOR Gd3+ IN La2-xSrxCuO4

The zero-field splitting D of the S-8(7/2) ground singlet for the tetragonal Gd3+ center in La2-xSrxCuO4 is theoretically studied from the superposition model. Meanwhile, the g factor is also quantitatively investigated from the approximation formula including admixture of the ground 8S7/2 and the excited L-6(7/2) (L=P, D, F, G) states via the spin-orbit coupling interactions. The calculated zero-field splitting and g factor are in reasonable agreement with the experimental data. It is found that the significant zero-field splitting can be ascribed to the average impurity-ligand bonding angles [approximate to (theta(1) + theta(2))/2 approximate to 62 degrees] related to the four-fold axis larger than that (approximate to 54.74 degrees) of the cubic case. Nevertheless, the experimental g factor close to 2 may be largely due to the very slight admixture of the ground 8S7/2 and the excited L-6(7/2) states via the spin-orbit coupling interactions.