EPR and ENDOR with Gd 3+ in Bi 2Mg 3(NO 3) 12·24H 20

Abstract

The parameters of the spin Hamiltonians of various isotopes of Gd 3+ in Bi 2 Mg 3-(NO 3) 12·24H 20 have been determined with EPR and ENDOR at T ≈ 1.5° K. The microwave frequency was approximately 9.3 GHz. Three higher-order hyperfine interaction terms could be distinguished. These were T 0 0( S 2 m , I 2 m ′, T 2 0( S 2 m , I 2 m′ ), and T 2 0( S 3 m, I 1 m′ , which have the same overall symmetries as the spherical harmonics Y 0 0, Y 0 2, and Y 2 0, respectively. The values of the parameters B 2 0 and F 0 0 of the terms [3 S z 2 − S( S + 1)] and and T 0 0( S 2 m , I 2 m′ ) respectively are also evaluated theoretically, using the same perturbation mechanisms for both cases. The signs of the theoretical values are correct, the magnitudes being reasonable but somewhat high, especially for F 0 0. It is argued that the theoretical interpretation of F 0 0 should be less complicated than that of B 2 0.