On unstable magnetic ordering in Ce 3d compounds and their hydrides

Abstract

57Fe Mössbauer, X-ray photoemission and Ce LIII edge X-ray absorption measurements on CeFe2, selected pseudobinaries Ce(Fe1 − yXy)2 and some of their hydrides were carried out to shed light on magnetic ordering in these materials. While the hydrides order ferromagnetically in the temperature range below Tc, a double transition is observed in the pseudobinaries. At Tc, ferromagnetic ordering sets in, followed by an antiferromagnetic phase below a lower-lying critical temperature Tc2, their magnetic ordering type having been found to be of some complexity. In the parent compounds, cerium is of a non-integral valency, i.e. it contains 4f0 admixture. On hydrogen absorption it changes to 3+, corresponding to 4f1.