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arXiv · 2212.12483

Adiabatic demagnetization cooling well below the magnetic ordering temperature in the triangular antiferromagnet KBaGd(BO3)2

A. Jesche·N. Winterhalter-Stocker·F. Hirschberger·A. Bellon·S. Bachus·Y. Tokiwa·A. A. Tsirlin·P. Gegenwart
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Abstract

Crystal structure, thermodynamic properties, and adiabatic demagnetization refrigeration (ADR) effect in the spin-7/2 triangular antiferromagnet KBaGd(BO3)2 are reported. With the average nearest-neighbor exchange coupling of 44 mK, this compound shows magnetic order below $T_N = 263$\,mK in zero field. The ADR tests reach the temperature of $T_{min} = 122$ mK, more than twice lower than $T_N$, along with the entropy storage capacity of 192 mJK$^{-1}$cm$^{-3}$ and the hold time of more than 8 hours in the PPMS setup, both significantly improved compared to the spin-1/2 Yb$^{3+}$ analog. We argue that KBaGd(BO3)2 shows a balanced interplay of exchange and dipolar couplings that together with structural randomness and geometrical frustration shift $T_{min}$ to well below the ordering temperature $T_N$, therefore facilitating the cooling.

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A. Jesche, N. Winterhalter-Stocker, F. Hirschberger, A. Bellon, S. Bachus, Y. Tokiwa, A. A. Tsirlin, P. Gegenwart. 2022-12-23. Adiabatic demagnetization cooling well below the magnetic ordering temperature in the triangular antiferromagnet KBaGd(BO3)2. https://doi.org/10.1103/physrevb.107.104402

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