Giant-Magnetocaloric effect and phonon dynamics in (GdCe)CrO$_3$

TL;DR

This study reveals a giant magnetocaloric effect and detailed phonon dynamics in Ce-doped GdCrO$_3$, highlighting spin reorientation, magnetic entropy change, and spin-phonon coupling in this orthorhombic perovskite.

Contribution

It demonstrates a significant magnetocaloric effect in Ce-doped GdCrO$_3$ and elucidates the spin reorientation and phonon interactions caused by Ce substitution.

Findings

Large magnetic entropy change (~45 J/kg-K) at 3 K for high magnetic fields.

Ce doping induces spin reorientation and field-induced irreversibility.

Pronounced spin-phonon coupling observed via vibrational mode analysis.

Abstract

We investigate the effect of Ce$^{3+}$ substitution on the magnetic ordering and phonon dynamics of the GdCrO$_3$ orthorhombic perovskite. The Ce doped compound exhibits long-range canted antiferromagnetism with Neel transitions, T$_N$ at $\sim$ 173 K, accompanied by spin-flip, T$_{SF}$ at $\sim$ 10 K. Ce$^{3+}$ incorporation drives a modification of the spin-flip transition from the $\Gamma{(G_x,A_y,F_z)}$ configuration to $\Gamma$ inducing a reorientation of the spin axis between the (001) and (001) crystallographic planes. This spin reorientation is governed by Zeeman energy and produces pronounced field-induced irreversibility between FCC and FCW magnetization processes. The substituted compound Gd$_{0.9}$Ce$_{0.1}$CrO$_3$ (GCCO) exhibits a remarkably large magnetic entropy change, $\Delta$ S $\sim$ 45-40 J/kg-K for $\Delta$ H = 90-70 kOe at 3 K among the highest reported for rare-earth orthochromites. The interplay of spin-only magnetocrystalline anisotropy from Cr$^{3+}$ and spin-orbit-driven magnetic moments of Gd$^{3+}$ and Ce$^{3+}$ results in pronounced spin-phonon coupling, manifested through the A$_{1g}$(6) vibrational mode. The observed temperature-dependent spectral evolution is consistent with behaviour reported in isostructural magnetic perovskites.