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Updated: May 9, 2026

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Published on: July 20, 2022
Quantum criticality enhanced millikelvin magnetic refrigeration in a large-spin-7/2 triangular lattice
Weijie Lin1,2,3, Nan Zhao4,5,6, Zhaoyi Li1,2,3
1Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
Abstract:
Large-spin (S) triangular lattice antiferromagnets exhibit both strong quantum fluctuations and high magnetic entropy, making them promising candidates for ultra-low-temperature magnetic refrigeration. In such materials, an external magnetic field can significantly influence the system's Hamiltonian, leading to the emergence of distinct magnetically ordered ground states. Interestingly, at the critical field between two ordered phases, the spins can develop a highly degenerate magnetic ground state, giving rise to enhanced quantum fluctuations and a pronounced magnetocaloric effect. In this study, the magnetic phase diagram of the S = 7/2 triangular lattice antiferromagnet GdBO3 was established through measurements of specific heat, magnetization, and the magnetocaloric effect. The phase diagram reveals that the system exhibits four distinct ground states (phases I, II, III, and IV) under external magnetic fields. Notably, a 1/3 magnetization plateau is observed in phase II, as indicated by the magnetization curve. Due to strong quantum fluctuations at critical field B c3 and the high density of magnetic Gd3+ ions, we achieved a minimum temperature of 50 mK using a custom-designed adiabatic demagnetization refrigerator. Our findings reveal significant quantum fluctuations below 2 K, demonstrating GdBO3's potential for millikelvin magnetic cooling applications.
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