Magnetism of 3d electrons in YCo12-xFexB6 compounds

The magnetic properties of the polycrystalline YCo12-xFexB6 alloys are thoroughly investigated through the scope of the Kuz'min model describing the thermal evolution of the spontaneous magnetization. The analysis of this behavior reveals a strong composition dependence of the magnetization as well as its thermal evolution. This is interpreted as an evolution from first neighbor ferromagnetic (FM) interactions with progressively reinforced antiferromagnetic (AFM) interactions. The magnetization in the ordered state decreases when increasing Fe content from 0.45 mu B/f.u. down to 0.11 mu B/f.u. for x = 0 and x = 4, respectively. The Inoue-Shimizu s-d model has also been used close to the ordering temperature to investigate the evolution of the Landau coefficients and study in detail the order of the magnetic transition and have some insights on the magnetovolume coupling in this series of compounds. It revealed that Fe for Co substitution causes the already weak magnetovolume exchange to become even weaker.