Rare-earth tuning of magnetic entropy and interaction scales in K3Ln(PO4)2 (Ln = Yb, Gd) for adiabatic demagnetization refrigeration
Abstract
Adiabatic demagnetization refrigeration (ADR) based on frustrated rare-earth magnets provides a promising route toward helium-free sub-Kelvin cooling, while balancing magnetic entropy and interaction scales is essential for optimizing the ADR functionalities. Here we investigate the low-temperature magnetic and ADR properties of the alkali rare-earth double phosphates K3Ln(PO4)2 (Ln = Yb, Gd), which crystallize in a monoclinic P21/m structure containing distorted isosceles triangular lattices of rare-earth ions. Magnetization and specific heat measurements confirm the absence of long-range magnetic ordering down to 0.1 K in both compounds. Direct quasi-ADR measurements demonstrate strongly contrasting refrigeration behaviors: K3Yb(PO4)2 reaches a minimum temperature of 29.8 mK from an initial state of 2 K and 6 T, whereas K3Gd(PO4)2 exhibits extended hold times below 150 mK associated with its larger magnetic entropy reservoir. Crystal-electric-field calculations confirm a Jeff = 1/2 ground-state doublet in K3Yb(PO4)2, while thermodynamic analysis based on magnetic entropy and interaction scales accounts for the distinct ADR performance of the two compounds. These results identify K3Ln(PO4)2 as a chemically robust platform for rare-earth-tunable solid-state ADR.
Versions
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BibTeX
@misc{wang2026rareearth,
title = {{Rare-earth tuning of magnetic entropy and interaction scales in K$_3$$Ln$(PO$_4$)$_2$ ($Ln$ = Yb, Gd) for adiabatic demagnetization refrigeration}},
author = {Yonglin Wang and Chuandi Zhang and Jianglong Zhang and Zihang Gao and Ziqi Li and Feiran Shen and Lunhua He and Peijie Sun and Hao Deng and Junsen Xiang and Wentao Jin},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.28038},
eprint = {2610.28038},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.28038},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Rare-earth tuning of magnetic entropy and interaction scales in K_3Ln(PO_4)_2 (Ln = Yb, Gd) for adiabatic demagnetization refrigeration
AU - Yonglin Wang
AU - Chuandi Zhang
AU - Jianglong Zhang
AU - Zihang Gao
AU - Ziqi Li
AU - Feiran Shen
AU - Lunhua He
AU - Peijie Sun
AU - Hao Deng
AU - Junsen Xiang
AU - Wentao Jin
PY - 2026
DA - 2026/10/20
PB - arXiv
DO - 10.48550/arxiv.2610.28038
UR - https://arxiv.org/abs/2610.28038
AB - Adiabatic demagnetization refrigeration (ADR) based on frustrated rare-earth magnets provides a promising route toward helium-free sub-Kelvin cooling, while balancing magnetic entropy and interaction scales is essential for optimizing the ADR functionalities. Here we investigate the low-temperature magnetic and ADR properties of the alkali rare-earth double phosphates K_3Ln(PO_4)_2 (Ln = Yb, Gd), which crystallize in a monoclinic P2_1/m structure containing distorted isosceles triangular lattices of rare-earth ions. Magnetization and specific heat measurements confirm the absence of long-range magnetic ordering down to 0.1 K in both compounds. Direct quasi-ADR measurements demonstrate strongly contrasting refrigeration behaviors: K_3Yb(PO_4)_2 reaches a minimum temperature of 29.8 mK from an initial state of 2 K and 6 T, whereas K_3Gd(PO_4)_2 exhibits extended hold times below 150 mK associated with its larger magnetic entropy reservoir. Crystal-electric-field calculations confirm a J_eff = 1/2 ground-state doublet in K_3Yb(PO_4)_2, while thermodynamic analysis based on magnetic entropy and interaction scales accounts for the distinct ADR performance of the two compounds. These results identify K_3Ln(PO_4)_2 as a chemically robust platform for rare-earth-tunable solid-state ADR.
ER -