Magnetocaloric Effect in Anisotropic Mixed Spin 12 –1 System: Pair Approximation Method

Abstract

We use the Pair Approximation method to analyze the magnetic and magnetocaloric behaviors of diluted mixed spin SA = 1 and spin SB = 1/2 with the anisotropic Heisenberg model, on a cubic lattice with coordination number z=6. Our system is described in presence of an external magnetic field; the phase diagram and thermodynamic properties related to the concentration of magnetic atom (A or B) and the single ion anisotropy are constructed and discussed. Special attention is paid to magnetocaloric properties provided by isothermal entropy change as well as the cooling capacity. These cooling power keys are plotted and discussed as a function of interaction anisotropy and magnetic component concentration of two sublattices ions A and B. Numerical results show a double peak structure in the entropy change curve and the inverse magnetocaloric effect related to the presence of the negative single-ion anisotropy.

The Pair Approximation method for the ferromagnetic Heisenberg model with spin $S=1$ and arbitrary range of interactions. Application for the magnetic semiconductor CrIAs

“…Regarding quantum models, apart from the pure Heisenberg [24,26], or mixed Heisenberg-Ising systems [28], the XXZ model with spin S = 1/2 [15] and the transverse Ising model with a random field [14] have been studied, together with XY model applied to describe a particular magnetocaloric material [32]. Recently, the anisotropic Heisenberg model with spin S = 1 has been investigated within this method [33] and also a mixed-spin system with spins 1/2 and 1 was investigated [34]. It is worth noticing that also some non-magnetic applications of PA have been developed, for example, for modelling of brain-computer interfaces [35].…”