Enhanced magnetocaloric effect from Cr substitution in Ising lanthanide gallium garnets $Ln_3\text{CrGa}_4\text{O}_{12}$ ($Ln$ = Tb, Dy, Ho)

TL;DR

This study demonstrates that substituting Cr into lanthanide gallium garnets significantly enhances their magnetocaloric effect at low magnetic fields, due to reduced magnetic frustration and altered ground states.

Contribution

It provides new insights into how Cr substitution improves magnetocaloric properties in Ising lanthanide garnets, with detailed structural and magnetic analysis.

Findings

Cr substitution increases MCE by 20% for Dy and 120% for Ho at low fields.

Cr reduces magnetic frustration in the garnet lattice.

Structural analysis confirms Cr incorporation alters magnetic ground states.

Abstract

A detailed study on the crystal structure and bulk magnetic properties of Cr substituted Ising type lanthanide gallium garnets $Ln_3\text{CrGa}_4\text{O}_{12}$ ($Ln$ = Tb, Dy, Ho) has been carried out using room temperature powder X-Ray and neutron diffraction, magnetic susceptibility, isothermal magnetisation and heat capacity measurements. The magnetocaloric effect (MCE) in $Ln_3\text{CrGa}_4\text{O}_{12}$ is compared to that of $Ln_3\text{Ga}_5\text{O}_{12}$. In lower magnetic fields attainable by a permanent magnet ($\leq$ 2 T), Cr substitution greatly enhances the MCE by 20% for $Ln$ = Dy and 120% for $Ln$ = Ho compared to the unsubstituted $Ln_3\text{Ga}_5\text{O}_{12}$. This is likely due to changes in the magnetic ground state as Cr substitution also significantly reduces the frustration in the magnetic lattice for the Ising type $Ln_3\text{Ga}_5\text{O}_{12}$.