Magnetocaloric properties of $R_3$Ga$_5$O$_{12}$ ($R$ = Tb,Gd,Nd,Dy)

TL;DR

This study compares the magnetocaloric properties of various rare-earth garnets to identify the most effective materials for low-temperature magnetic refrigeration, highlighting Dy$_3$Ga$_5$O$_{12}$ as particularly promising.

Contribution

The paper provides a comparative analysis of magnetocaloric properties of several rare-earth garnets, suggesting potential improvements over GGG for low-temperature ADR applications.

Findings

Dy$_3$Ga$_5$O$_{12}$ shows optimal RCP at low fields and temperatures.

Nd$_3$Ga$_5$O$_{12}$ has lower transition temperatures due to de Gennes factor.

Tb$_3$Ga$_5$O$_{12}$ offers higher saturation magnetization.

Abstract

We report the characteristic magnetic properties of several members of the rare-earth garnet family, Gd$_3$Ga$_5$O$_{12}$ (GGG), Dy$_3$Ga$_5$O$_{12}$ (DGG), Tb$_3$Ga$_5$O$_{12}$ (TGG), and Nd$_3$Ga$_5$O$_{12}$ (NGG), and compare their relative potential utility for magnetocaloric cooling, including their minimal adiabatic demagnetization refrigeration (ADR) temperatures and relative cooling parameters. A main objective of this work concerns the identification of potential improvements over the magnetocaloric properties of GGG for use in low temperature ADR cryostats. Using Tb$^{+3}$ and Dy$^{+3}$ in the rare-earth site offers, in principle, a higher saturation magnetization and Nd$^{+3}$ gives a lower de Gennes factor and therefore potentially reduced magnetic transition temperatures, limiting the useful temperature range. Our results show that Dy$_3$Ga$_5$O$_{12}$ yields an optimal relative cooling parameter ($RCP$) at low applied fields and low limiting temperatures, which would allow for the design of more efficient ADR cryostats.