Exchange and CEF interactions in R2Fe14B compounds

Abstract

The magnetic properties of R ions in R₂Fe₁₄B compounds (R=rare earth, Th) are determined by a combination of R‐Fe exchange and crystalline electric field interactions. A comparison of the ordering temperatures of all compounds in the series shows that the exchange interactions between R and Fe moments are not simply proportional to the spin moments but there is a decrease across the series, with interactions for compounds with light R elements enhanced by a factor of 2 compared to those with heavy R elements. This decrease is related to the decrease of 4f‐5d exchange interactions within the R ions. The second‐order and fourth‐order terms of the crystalline electric field potential of the environment have been obtained in a number of compounds from analysis of their magnetic properties (Nd, Er, Tm, Yb). Scaling the values obtained for other compounds (Pr, Sm, Ho,...) results in a fairly good description of their magnetic properties.