A theoretical model is presented for the calculation of the magnetic properties of generalised spin ferrimagnetic random substitutional alloys AcB1-c with antiferromagnetic couping between the A and B spin species. In particular, we study in an effective field method the phase diagrams of these systems as a function of the alloy concentration c, for given magnetic exchange constants. The model is applied with no adjustable parameters to the transition metal-rare-earth FecGd1-c and FecTb1-c alloys, using the appropriate spins for the Fe, Gd and Tb ions. We report a coherent and an overall qualitative agreement between theory and experiment in the complete range of concentrations 1 ≥ c ≥ 0, for the first time to our knowledge, and determine consequently for these materials a set of ionic exchange constants that are invariant with respect to the alloy concentration. To our knowledge this is the first time that approximate but seemingly reliable exchange constants for the two alloys have been derived.
ASJC Scopus subject areas
- Condensed Matter Physics