Large low-field magnetocaloric response in a ferromagnetic gadolinium orthophosphate

TL;DR

This study demonstrates that ferromagnetic gadolinium orthophosphates exhibit a significant magnetocaloric effect at low magnetic fields, making them promising candidates for magnetic refrigeration applications.

Contribution

The paper reports the discovery of a large low-field magnetocaloric response in Gd orthophosphate, supported by experimental and mean-field calculations, highlighting its potential for low-field magnetic refrigeration.

Findings

Large magnetic entropy change of 36.2 J kg-1 K-1 at 2 T and 2 K.

Maximum adiabatic temperature change of 10.9 K.

No magnetic ordering observed until 2 K.

Abstract

Bulk magnetic and thermodynamic measurements, along with mean-field calculations, were conducted on the ferromagnetic K3Gd5(PO4)6 powders. No magnetic ordering was observed until 2 K, while the application of an external field B > 1 T resulted in the splitting of the Gd3+ ground state multiplet and induced a non-cooperative Schottky effect. The average nearest-neighbor exchange strength |J1/kB| is determined to be 0.017 K, which leads to a remarkably large low field magnetic entropy change {\Delta}Sm = 36.2 J kg-1 K-1 under applied field change B = 2 T at temperature T = 2 K, as well as a maximum adiabatic temperature change Tad = 10.9 K. We contend that ferromagnetic gadolinium orthophosphates serve as a promising reservoir for exploring advanced magnetic refrigerants applicable under low magnetic fields.