Theoretical analysis of magnetic properties and the magnetocaloric effect using the Blume-Capel model

TL;DR

This paper provides a theoretical analysis of the magnetic properties and magnetocaloric effect in the spin-1 Blume-Capel model using mean-field theory, highlighting phase transitions and entropy variations.

Contribution

It introduces a detailed mean-field theoretical framework to analyze magnetocaloric effects and phase transitions in the Blume-Capel model, including the use of Maxwell and Clausius-Clapeyron relations.

Findings

Identification of first-order and continuous phase transitions.

Calculation of entropy changes related to the magnetocaloric effect.

Demonstration of the model's applicability to understanding magnetic entropy variations.

Abstract

This work investigates the magnetic properties and the magnetocaloric effect in the spin-1 Blume-Capel model. The study was carried out using the mean-field theory from the Bogoliubov inequality to obtain the expressions of free energy, magnetization and entropy. The magnetocaloric effect was calculated from the variation of the entropy obtained by the mean-field theory. Due to the dependence on the external magnetic field and the anisotropy included in the model, the results for the magnetocaloric effect provided the system with first-order and continuous phase transitions. To ensure the results, the Maxwell relations were used in the intervals where the model presents continuous variations in magnetization and the Clausius-Clapeyron equation in the intervals where the model presents discontinuity in the magnetization. The methods and models for the analysis of a magnetic entropy change and first-order and continuous magnetic phase transitions, such as mean-field theory and the Blume-Capel model, are useful tools in understanding the nature of the magnetocaloric effect and its physical relevance.