Magnetocaloric effect and critical behavior near the paramagnetic to ferrimagnetic phase transition temperature in TbCo2-xFex

TL;DR

This study investigates the magnetocaloric effect and critical behavior near the phase transition in TbCo2-xFex, revealing how Fe substitution tunes transition temperature, broadens operating range, and alters universality class.

Contribution

It demonstrates Fe substitution's effect on transition temperature, magnetic entropy change, and universality class in TbCo2-xFex, providing insights for magnetic refrigeration applications.

Findings

Fe substitution increases transition temperature to near room temperature.

Maximum magnetic entropy change is 3.7 J/kg·K for TbCo1.9Fe0.1 at 5 T.

Critical exponents shift from 3D Heisenberg to mean-field with Fe doping.

Abstract

Magnetocaloric effect (MCE) in TbCo2-xFex has been studied by dc magnetization measurements.On substituting Fe in TbCo2, not only the magnetic transition temperature is tuned to room temperature, but also the operating temperature range for MCE is increased from 50 K for TbCo2 to 95 K for TbCo1.9Fe0.1. The maximum magnetic entropy change (-{\Delta}SM) for TbCo1.9Fe0.1 is found to be 3.7 J kg-1 K-1 for a 5 T field change, making it a promising candidate for magnetic refrigeration near room temperature. The temperature dependent neutron diffraction study shows a structural phase transition (from cubic to rhombohedral phase with lowering of temperature) which is associated with the magnetic phase transition and these transitions broaden on Fe substitution. To investigate the nature of the paramagnetic to ferrimagnetic phase transition, we performed a critical exponent study. From the derived values of critical exponents, we conclude that TbCo2 belongs to the 3D Heisenberg class with short-range interaction, while on Fe substitution it tends towards mean-field with long-range interaction. The derived values of critical exponents represent the phenomenological universal curve for the field dependence of {\Delta}SM, indicating that TbCo2 and TbCo1.9Fe0.1 belong to two different universality classes.