CRYSTAL-FIELD AND MAGNETIC-PROPERTIES OF THE DISTORTED PEROVSKITE NDGAO3

Inelastic neutron scattering and magnetic susceptibility measurements have been performed on the distorted perovskite NdGaO3. The magnetic susceptibility data show a Curie-Weiss behaviour with an effective magnetic moment close to 3.6 mu(B) per mole of Nd ions. No long--> range magnetic ordering was detected in the temperature range 2-300 K. The inelastic neutron spectra observed at T = 12 K exhibit four peaks of magnetic origin between 11 and 70 meV which can be unambiguously assigned to the complete crystalline-electric-field splitting pattern in the ground-state J multiplet I-4(9/2) Of the Nd3+ ions. We analysed the spectra in terms of geometrical considerations based on the actual C-2 site symmetry of Nd3+. The best agreement between the experimental spectra and the calculated level structure was obtained for a model that takes into account the three nearest-neighbouring coordination polyhedra associated with the 0(2-), Ga3+ and Nd3+ ions as well as J-mixing between all multiplets of the I-4 term. We conclude that single-particle crystal-field theory adequately explains the majority of magnetic and crystal-field properties of NdGaO3.