Polarized neutron investigation in the mixed-valence compound Sm_3Te_4

摘要

Cubic Sm_3Te_4 can be characterized as a semiconducting, inhomogeneous mixed-valence system. No evidence of charge ordering is found at low temperature, indicating that Sm~(2+) and Sm~(3+) ions are randomly distributed on one crystallographic position. The magnetization density of a Sm_3Te_4 single crystal was measured at 1.5 K using polarized neutrons, with a magnetic field applied along [110]. As the Sm_3Te_4 structure is not centric, the measured flipping ratios have been directly processed by the maximum entropy method and by a least-squares refinement. The two approaches are in agreement: under the action of the magnetic field, the Sm site splits into two subsites, with very different induced magnetization densities. Two possible explanations are proposed.