Unveiling a Scaling and Universal Behavior for the Magnetocaloric Effect in Cubic Crystal Structures: A Monte Carlo Simulation

J D Alzate-Cardona,J S Salcedo-Gallo,D F Rodríguez-Patiño,C D Acosta-Medina,E Restrepo-Parra

doi:10.1038/s41598-019-41321-y

J D Alzate-Cardona, J S Salcedo-Gallo + Show 3 more

Open Access

https://doi.org/10.1038/s41598-019-41321-y

Copy DOI

Journal: Scientific Reports	Publication Date: Mar 26, 2019
Citations: 5	License type: open-access

Affiliation: Universidad Nacional de Colombia

Abstract

The magnetocaloric effect and the universal character for the magnetic entropy change regarding the cubic crystal structures (SC, BCC, FCC) were investigated, in a qualitative way, using Monte Carlo simulations. A classical Heisenberg Hamiltonian with nearest neighbors, and next nearest neighbors interactions was implemented. In order to compute the critical temperature of the system depending on the coordination number, it was calculated the dependence of the magnetization and magnetic susceptibility as a function of temperature. Magnetic field dependence on the magnetization for isothermal processes was performed considering a magnetocrystalline anisotropy term. In this way, the magnetic entropy change (ΔSm) was computed. Results show that the rescaled ΔSm as well as the exponent (n) characterizing the field dependence of the magnetic entropy change curves, collapse onto a single curve for the studied crystal structures. By this reason, it can be assured that ΔSm exhibits a universal behavior regarding the strength and contribution of the magnetic exchange energy to the total magnetic energy.

Highlights

In recent years, it has been invested a great effort on correlating ΔSm with the critical exponents of the ferromagnetic-paramagnetic phase transition[14,15,16,17]; by knowing the denominated phenomenological universal curve for ΔSm, it is possible to predict the behavior of ΔSm for ferromagnetic alloys of the same compositional series or for the same material at different applied magnetic fields
It can be observed that, as the coordination number increases, the critical temperature increases. This is due to the fact that the exchange energy increases as the coordination number increases and, more thermal energy is required to break the magnetic ordering imposed by the exchange interactions and to reach the paramagnetic regime
It can be seen that the peak of the susceptibility curves decreases when the interaction of the next nearest neighbors (NNN) (Fig. 1b) is taken into account

Summary

Introduction

It has been invested a great effort on correlating ΔSm with the critical exponents of the ferromagnetic-paramagnetic phase transition[14,15,16,17]; by knowing the denominated phenomenological universal curve for ΔSm, it is possible to predict the behavior of ΔSm for ferromagnetic alloys of the same compositional series or for the same material at different applied magnetic fields.

Results

Conclusion