The magnetic structure in the antiferromagnetic phase of Ce(Fe1-xCox)2

Abstract

The nature of the low-temperature (T approximately=90 K) magnetic phase transition in cubic Laves-phase Ce(Fe1-xCox)2 compounds with x=0.15, 0.20 has been determined using powder neutron diffraction measurements. Below this temperature, ferromagnetism is replaced by an antiferromagnetic phase, which consists of (111)-type sheets with parallel spins and antiparallel coupling of spins between adjacent (111) sheets. The orientation of the magnetic moments could not be uniquely determined; however, they are oriented within a cone that is defined by sin2 phi =2/3 relative to the (111) sheets and includes the (Fe, Co) sublattice nearest-neighbour directions. No difference in magnitude between the (Fe, Co) sublattice moments of the two phases could be detected, nor was any significant magnetic moment detected at the Ce sites in either phase. High-resolution neutron diffraction measurements show that the application of large magnetic fields ( approximately=4T) in the antiferromagnetic phase restores ferromagnetism and removes the associated structural distortion.