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

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.