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

E. Riordan, E. Lhotel, N. -R. Camara, C. Marin, M. E. Zhitomirsky

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 $ΔS_m$, 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.

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

Abstract

The magnetocaloric effect in the quantum dipolar magnet YbGaO is studied both for pure material and with non-magnetic substitution: (YbY)GaO. Magnetization measurements have been performed on a single crystal, , and on powder samples with 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 , a key figure of merit for adiabatic demagnetization refrigeration, has been derived from the magnetization data. The 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.
Paper Structure (5 sections, 2 equations, 4 figures)

This paper contains 5 sections, 2 equations, 4 figures.

Table of Contents

  1. Author declaration
  2. Acknowledgements
  3. References

Figures (4)

  • Figure 1: Field dependence of the magnetization for diluted YbGG at several temperatures. Blue symbols show the experimental data for the 20% diluted sample, red symbols represent the 40% diluted sample. Inset: Inverse volumic susceptibility as a function of temperature for the two diluted samples with fits to a Curie-Weiss law (black lines). The 20% diluted data is in a field of 0.1 T, the 40% sample data contain results for 0.1 T, 0.2 T and 0.4 T fields, which are all in the linear regime.
  • Figure 2: Magnetization versus temperature for the 20% diluted YbGG. Symbols represent the experimental data and black lines show the analytical fits.
  • Figure 3: Isothermal entropy variations $\Delta S_m$ of pure YbGG compared to the reference magnetocaloric materials: FAA, Wikus2014 and GGG. Fisher1973
  • Figure 4: Comparisons of $\Delta S_m$ between the pure sample (dashed lines in both) the 20% sample (top figure dashed lines) and the 40% sample (bottom figure dashed lines)