Room Temperature Magnetocaloric Effect In CrTe1-XSex Alloys

TL;DR

This study investigates the magnetocaloric effect in CrTe1-xSex alloys at room temperature, revealing significant entropy changes and RCP values, with phase transitions characterized by critical exponents indicating second order magnetic phase transitions.

Contribution

It provides new insights into the room temperature magnetocaloric properties of CrTe1-xSex alloys and details their critical behavior, which was not previously characterized.

Findings

Maximum magnetic entropy change around 8.3-9.2 J/kg.K.

Relative cooling power up to 694 J/kg.

Second order phase transition with 3D Mean field critical exponents.

Abstract

Polycrystalline CrTe1-xSex samples were prepared using the conventional solid-state reaction technique and characterized by x-rad diffraction, temperature- and field- dependent magnetization for possible use in magnetocaloric cooling. Rietveld refinement revealed two phases in all prepared samples; a minor monoclinic phase that decreases with Se concentration until it vanishes near 10% of Se, and a major hexagonal one. At high temperature, CrTe1-xSex is paramagnetic, with ferromagnetic phase transition occurs at Tc ~332, 320, 318, 310, 299, and 295 K for x= 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10, respectively. The magnetocaloric effect analysis (at H=5T) revealed a maximum magnetic entropy change of about 8.3, 7.9, 8.2, 9.1, 9.2, and 8.5 (J/kg.K) with a relative cooling power (RCP) value of about 555, 568, 547, 638, 694, and 668 (J/kg) around Tc for x= 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10, respectively. Critical behavior analysis showed that the magnetic isotherms measured near Tc follow 3D Mean field critical exponents and a second order phase transition. A rigorous iteration estimated the critical exponents based on modified Arrott and Kouvel-fisher plots analysis, giving $\beta$ ~ 0.44, 0.51, 0.46, 0.49, 0.42, 0.49 and $\gamma$ ~ 1.02, 1.00, 0.99, 1.08, 1.07, 0.96, and 1.01 for x= 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10, respectively.