Exchange interactions and crystal-field effects in HoX (X=AgX=Ag, Cd, Cu, Mg, Rh, Zn) intermetallic compounds

We present an ab initio treatment of the exchange interactions and crystal-field effects in HoX (X=AgX=Ag, Cd, Cu, Mg, Rh, Zn) intermetallic compounds with the CsCl crystal structure. The exchange interactions are determined using the magnetic-force theorem starting from both a ferromagnetically ordered state (zero temperature) and a disordered-local-moments (effectively high temperature) state up to an interatomic distance of 10a10a, where a is the lattice parameter. The exchange interactions are used for construction of the Heisenberg Hamiltonian, from which we determine the magnetic-transition temperatures using the mean-field approximation and the Green's-function based random-phase approximation. The crystal-field parameters are derived from an ab initio electronic structure of the non-magnetic state. A combined Hamiltonian is treated within the mean-field approximation to study the effect of the crystal-field interaction on the critical temperatures and the magnetization.