The Shastry-Sutherland lattice is a prototypical frustrated quantum magnet. It is notable for its exactly solvable dimer-singlet ground state and hosts a wealth of magnetic phenomena under external fields. Here, this work investigates the high-spin (S = 7/2) Eu-based magnet Eu2MgSi2O7 (EMSO) using low-temperature magnetothermal measurements and Monte Carlo simulations, revealing a giant magnetocaloric effect (MCE) in this Shastry-Sutherland compound. The entropy change peak value is found to be 55.0 J kg-1 K-1 under a field change of B = 0-4 T, approximately 1.5 times larger than the commercial Gd3Ga5O12 (GGG). Adiabatic demagnetization refrigeration achieves a lowest temperature of 151 mK, deeply into the sub-Kelvin regime. Furthermore, a distinctive cooling effect persists below about 1 T, a characteristic absent for conventional magnetic coolants. A dipolar Shastry-Sutherland model is introduced as a minimal model to describe this system; in particular, the experimentally revealed 1/3 magnetization pseudo-plateau can be ascribed to the presence of dipolar couplings between Eu2+ ions, further stabilized by the thermal fluctuations, explaining the persistent cooling effect. This work establishes EMSO as a novel platform for exploring the dipolar Shastry-Sutherland system and for sub-Kelvin adiabatic demagnetization refrigeration.
@article{arxiv.2602.08497,
title = {Giant Magnetocaloric Effect in a High-Spin Shastry-Sutherland Dipolar Magnet},
author = {Jianjian Gong and Junsen Wang and Junsen Xiang and Zhaojun Mo and Lei Zhang and Xinyang Liu and Xuetong He and Lu Tian and Zhixing Ye and Huicai Xie and Xucai Kan and Xinqiang Gao and Zhenxing Li and Peijie Sun and Shouguo Wang and Wei Li and Baogen Shen and Jun Shen},
journal= {arXiv preprint arXiv:2602.08497},
year = {2026}
}