Strongly anisotropic magnetocaloric effect in a dipolar magnet LiGdF$_4$

TL;DR

This study reveals a highly anisotropic magnetocaloric effect in LiGdF$_4$, with potential to improve magnetic refrigeration efficiency at cryogenic temperatures by exploiting directional magnetic properties.

Contribution

It provides a detailed experimental analysis of the anisotropic MCE in LiGdF$_4$ single crystals and interprets the results using a molecular field model, advancing understanding of anisotropic magnetocaloric materials.

Findings

MCE is highly anisotropic, with twice the efficiency along the c-axis.

Entropy change measurements are consistent with a molecular field model.

Results suggest potential for enhanced magnetic refrigeration at 2-10 K.

Abstract

We report the detailed study of the magnetocaloric effect (MCE) in a dipolar-Heisenberg magnet LiGdF$_4$ using magnetization measurements performed on a single crystal sample. Entropy variation on isothermal demagnetization from the magnetic field up to 3 T is determined in the temperature range 2-10 K for two principal directions of the applied field (parallel and perpendicular to the tetragonal $c$-axis of the crystal). The MCE is found to be highly anisotropic, with the cooling efficiency being up to twice higher at $H\parallel c$. The results are nicely interpreted in the frame of a conventional molecular field approach taking into account considerable anisotropy of the paramagnetic Curie-Weiss temperature. These results are compared to earlier studies of MCE in powder samples of LiGdF$_4$ [T. Numazawa et al., AIP Conf. Proc. 850, 1579 (2006)] as well as with analogous data for other well known magnetocaloric materials. Our findings may open new possibilities to enhance the efficiency of magnetic refrigeration in the liquid helium-4 temperature range.