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.
@article{arxiv.2405.20714,
title = {Large low-field magnetocaloric response in a ferromagnetic gadolinium orthophosphate},
author = {Ziyu W. Yang and Jie Zhang and Maocai Pi and Xubin Ye and Chenxu Kang and Xiaoliang Weng and Wei Tang and Hongzhi Cui and Yu-Jia Zeng and Youwen Long},
journal= {arXiv preprint arXiv:2405.20714},
year = {2024}
}