Neutron Diffraction Study Of USb: The Ordered State
Abstract
The elastic magnetic neutron cross section from a single crystal of USb has been measured in the antiferromagnetic state (type-I ordering, TN=241.2 K) for all Bragg reflections with sinθλ=κ4π<0.811 -1. By using the tensor-operator method, we have calculated the theoretical cross sections from a number of possible ground-state configurations and compared them with experiment. Excellent agreement is obtained for one model only; a 5f3 ionic state (U3+) with a Γ8(1) crystal-field ground state. Such a crystal-field ground state implies that the fourth-order crystal-field potential V4 is negative, which is the opposite sign to that found in the analogous 4f3 neodymium compounds. By measuring the temperature dependence of the magnetic scattering as a function of κ→ the scattering vector, we have been able to estimate the magnitude of the crystal-field parameters as V4-300 K, and V6-15 K. The implications of this first unambiguous identification of the electronic ground state in a metallic actinide compound are discussed. © 1976 The American Physical Society.
