Structural and magnetic properties of Cr_(1+x)(Se_(1-y)Te_y)_2 compounds

摘要

The structural and magnetic properties of Cr_(1+x)(Se_(1-y)Te_y)_2 having a NiAs structure has been studied for (1 + x) = 1.27, 1.32 and 1.36 and y = 0.75 by means of the Korringa-Kohn-Rostoker (KKR) band structure method. The sub-stoichiometry and the disorder on the chalcogenide sub-lattice has been treated by means of the coherent potential approximation (CPA) alloy theory. From total energy calculations a preferential site occupation on the Cr sub-lattice was found together with an antiparallel alignment of the magnetic moments on the two inequivalent Cr layers. The magnetic properties at finite temperature has been studied by means of Monte Carlo simulations on the basis of a classical Heisenberg Hamiltonian and the exchange coupling parameters calculated from first principles. This approach allowed to determine the critical temperature in good agreement with experiment.