Unveiling the potential of NdPO4 magnetocaloric phases in cryogenic refrigeration

TL;DR

This study demonstrates that NdPO4 phases, synthesized via a simple process, exhibit promising magnetocaloric properties at cryogenic temperatures, making them potential candidates for low-temperature magnetic cooling applications.

Contribution

The paper reveals that nanostructured NdPO4 phases have significant magnetocaloric effects near 3 K, highlighting their potential in cryogenic refrigeration.

Findings

NdPO4 nanorods have diameters of 10-20 nm and lengths of 200-500 nm.

Heat treatment transforms NdPO4 structure from hexagonal to monoclinic.

Monoclinic NdPO4 exhibits a magnetocaloric effect of about 19 J/kg K under 5 T near 3 K.

Abstract

The RPO4 orthophosphates (R = rare earth element) have recently attracted a wide interest due to the strong coupling between their electronic, orbital and structural ordering parameters resulting in a variety of functional properties. Herein, we demonstrate that NdPO4 phases synthesized via a facile precipitation growth process unveil promise in low-temperature magnetic cooling. The analysis of their structural properties reveals nanorod forms with diameters of 10 to 20 nm and lengths ranging from 200 to 500 nm while the heat treatment transforms their hexagonal rhabdophane-type structure to a monoclinic anhydrous monazite-type symmetry. Magnetization measurements and DFT calculations show strong antiferromagnetic couplings and the absence of any magnetic ordering in the 2-300 K range. On the other hand, the monoclinic phase of NdPO4 exhibits a large magnetocaloric effect of about 19 J/kg K under 5 T near 3 K, outperforming some reference materials containing more expensive rare-earth elements with high magnetic moments.