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

Jesche, A.*; Winterhalter-Stocker, N.*; Hirschberger, F.*; Bellon, A.*; Bachus, S.*; Tokiwa, Yoshifumi  ; Tsirlin, A. A.*; Gegenwart, P.*

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