Magnetocaloric Effect of Pure and Diluted Quantum Magnet Yb${}_3$Ga${}_5$O${}_{12}$

Abstract

The magnetocaloric effect in the quantum dipolar magnet Yb${}_3$Ga${}_5$O${}_{12}$ is studied both for pure material and with non-magnetic substitution: (Yb${}_{1-x}$Y${}_x$)${}_3$Ga${}_5$O${}_{12}$. Magnetization measurements have been performed on a single crystal, $x=0$, and on powder samples with $x=0.2$ and 0.4 in the temperature range between 70 mK to 300 K and in magnetic fields up to 8 T. The magnetic entropy change $\Delta S_m$, a key figure of merit for adiabatic demagnetization refrigeration, has been derived from the magnetization data. The $x=0.2$ sample exhibits the volumetric entropy variation comparable to, and at low fields even enhanced relative to, the pure compound. In contrast, the 40\%\ diluted sample shows a reduced effect, consistent with the conventional dilution picture. The Curie-Weiss law fits reveal positive Curie temperatures in both diluted samples, indicating the persistence of ferromagnetic correlations. The robustness of the magnetocaloric response upon moderate dilution highlights the potential of YbGG-based materials for low-temperature magnetic cooling applications, particularly in addressing thermal conductivity challenges through the chemical substitution without compromising cooling power.

4 pages, 4 figures