Uma revisão do efeito magnetocalórico em uma cadeia de spins distorcida com topologia diamante

Abstract

The magnetocaloric effect (MCE) occurs in some materials, characterized by the heating or cooling of the material when it interacts with a magnetic field. The thermodynamic process consists of the variation in entropy in an isothermal process and variation in temperature in an adiabatic process, as a function of the temperature for a given variation in the applied magnetic field. In recent years, several studies have been carried out to investigate this effect in hybrid spin systems. In this work we present a review of the EMC in a spin chain with diamond topology. The interaction between the first spin neighbors present in a chain is mediated by a pair of interstitial electrons that can jump between the interstitial sites of the chain. The kinetic energy associated with this quantum jump is given by the hopping amplitude, obeying the Pauli exclusion principle. Furthermore, we consider a distorted chain, that is, the interactions of the nodal sites with the interstitial sites, upper and lower, are different. Using the techniques of decoration-iteration, matrix-transfer and diagonalization, we find the Hamiltonian of the system, as well as its partition function, presenting below the fundamental state and thermodynamic quantities of the system. Finally, we analyzed the magnetocaloric effect of the model through the isentropy curves, magnetocaloric rate and isothermal entropy variation.