Direct Observation of an Incommensurate Multipolar Order in CeB6 Doped with Pr

Abstract

Observations on an ordered alloy Ce 0.7 Pr 0.3 B 6 by non-resonant X-ray diffraction are reported. We find incommensurate reflections (2δ, 1/2, 0) (δ∼0.23) below about 3 K in zero applied magnetic field. The wave vector dependence of the intensity is compelling evidence for the first direct observation of an incommensurate multipolar ordering (MPO). The incommensurate MPO appears to coexist with a commensurate MPO with a wave vector (1/2, 1/2, 1/2), which is the ground state configuration. Additional insight to the properties is derived from extensive measurements made with the alloy placed in a magnetic field ranging up to 6 T. We propose that a competition among RKKY-like exchange interactions between the Ce–Ce, Ce–Pr, and Pr–Pr multipoles is a main source for the appearance of the incommensurate MPO.