Frustrated magnet for adiabatic demagnetization cooling to milli-Kelvin temperatures

Abstract

Generation of very low temperatures has been crucially important for applications and fundamental research, as low-temperature quantum coherence enables operation of quantum computers and formation of exotic quantum states, such as superfluidity and superconductivity. One of the major techniques to reach milli-Kelvin temperatures is adiabatic demagnetization refrigeration. This method uses almost non-interacting magnetic moments of paramagnetic salts where large distances suppress interactions between the moments. The large spatial separations are facilitated by water molecules, with a drawback of reduced stability of the material. Here, we show that the water-free frustrated magnet KBaYb(BO3)2 can be ideal for refrigeration, achieving at least 22 mK. Compared to conventional refrigerants, KBaYb$${({{\rm{BO}}}_{3})}_{2}$$ ( BO 3 ) 2 does not degrade even under high temperatures and ultra-high vacuum. Further, its magnetic frustration and structural randomness enable cooling to temperatures several times lower than the energy scale of magnetic interactions, which is the main limiting factor for the base temperature of conventional refrigerants.

Chirality and Magnetocaloricity in GdFeTeO6 as Compared to GdGaTeO6

“…This makes GdFeTeO 6 attractive for the working body of low-temperature magnetic refrigerator devices. With the intensification of research at helium temperatures, the problem of cooling the current leads of superconducting solenoids and reaching ultralow temperatures becomes increasingly urgent [32][33][34][35][36][37].…”

Dipolar Spin Liquid Ending with Quantum Critical Point in a Gd-based Triangular Magnet

“…The scenario of DSL ending up with emergent U(1) QCP may also be applicable to other dipolar quantum magnets. Recent progress in experimental studies reveal a series of rare-earth triangular quantum dipolar antiferromagnets, e.g., Ba 3 REB 3 O 9 /Ba 3 REB 9 O 18 (with RE a rare-earth ion) [32,33] and ABaRE(BO 3 ) 2 (with A an alkali ion) [67,68]. For exam-ple, it has been observed that in Ba 3 YbB 3 O 9 that 80% entropy remain below 56 mK [31], despite a dipolar interaction of about 160 mK, suggesting that the DSL and unconventional QCP may also be relevant in the Yb-based dipolar compounds.…”

Enhancing the performance of magnetic refrigerants through tuning their magnetism from antiferromagnetism to weak ferromagnetism

“…Although it is known that high magnetic density and paramagnetic or weak ferromagnetic interactions are beneficial to obtaining the large-MCE magnetic refrigerants [16,17], owing to paramagnetic refrigerants often requiring relatively large fields to obtain large MCE [18], the key to obtaining large-MCE magnetic refrigerants under a low magnetic field is to prepare magnetic refrigerants with high magnetic density and weak ferromagnetic exchange simultaneously [19]. Although significant progress has been made in reducing magnetic interactions of magnetic refrigerants by introducing non-magnetic metal ions to separate magnetic metal ions [20][21][22][23], or anions with a high oxidation state of the central atoms [24,25] or long magnetic exchange bridges [26,27] to coordinate with Gd 3+ ions, efforts to obtain weak ferromagnetic refrigerants have been almost stalled.…”