CLUSTER-VARIATION-METHOD SIMULATIONS OF THE M1-XMX'PT-3 (M,M'=MN, FE, CO) MAGNETIC PHASE DIAGRAMS WITH COMPETING MAGNETIC INTERACTIONS

摘要

The alloying of isomorphic L1(2) ferromagnetic CoPt3, MnPt3 and antiferromagnetic FePt3 yields pseudobinary (M1-xMx'Pt-3) compounds whose magnetic phase diagrams display paramagnetic, ferromagnetic, antiferromagnetic, spin glass, and reentrant spin glass regions, depending on concentration and temperature. We show that it is possible to reproduce many features of these phase diagrams, namely, the Curie and Neel temperatures, using a simple Ising Hamiltonian, treated in the pair approximation of a square cluster-variation method, with only three dominant magnetic interactions between 3d elements, the magnetic role of Pt being neglected. The homoatomic interactions (J(MM), J(M'M')) are given by the magnetic transitions of the binary compounds, whereas the heteroatomic J(MM') interaction is either parametrized or fitted and left free to vary with concentration. [References: 16]