Efeito magnetocalórico em uma cadeia de Ising com interações de primeiros (diluídas) e segundos vizinhos

Abstract

The magnetocalloric effect (MCE) consists in the absorption or release of heat by a magnetic material under an external magnetic field change. The thermodynamical process by which it occurs is labeled as adiabatic demagnetization, intrinsically associated with the isothermal magnetic entropy change and the adiabatic temperature change of the material. Recently, theoretical and experimental research explored this effect in magnetic materials that present magnetic frustration and diluted= systems, characteristics that can amplify the magneticalloric effect. Our contribution make the scene by an Ising linear chain with first (whose spin sites are randomly diluted) and second neighbour interactions presenting competitive exchange interactions. In this system, we take account the possibility of the presence (or not) of the spin sites which interact via first neighbour interactions through the chain. From the exact results of the model, attained by the lowest energy found in the hamiltonian and transfer matrix techinique to obtain the grand canonical partition function, we could present the ground state and compute the thermodynamical quantities. Thus, we investigated the contribution of the dilution on site in the chain in two cases with different exchange interactions competitive scenario, exhibiting for both the influence upon the magnetization, entropy and the magnetocalloric effect through the isothermal entropic change