High-field magnetisation of RCo 9Si 2 compounds

Abstract

We prepared RCo 9Si 2 compounds in polycrystalline form with R representing Sm, Gd, and Tb. The magnetisation in fields up to 35 T was studied at 4.2 K on powder particles free to orient in the applied magnetic field. The Sm compound is ferromagnetic, the Gd and Tb compounds were found to order ferrimagnetically. The moments on the Co-sublattice are found to be about 0.9 μ B/Co-atom. For the ferrimagnetic samples, the exchange-coupling constant J RT/ k can be estimated from the slope of the high-field magnetic isotherm. This coupling constant is found to be 6.8 K for both the Gd and the Tb compound. To achieve a proper description of the magnetisation of TbCo 9Si 2 a three-sublattice model is used.