Enhancement in magnetocaloric properties of holmium chromite by gadolinium substitution

HoCrO3, Ho0.67Gd0.33CrO3, and GdCrO3 bulk powder samples were prepared by citrate route. The phase purity and the structural properties of the samples were examined by x-ray diffraction and Raman spectroscopic measurements. The dc magnetization data revealed that the Cr3+ ordering temperatures (Neel temperature) for the HoCrO3, Ho0.67Gd0.33CrO3, and GdCrO3 samples are 140K, 148K, and 167K, respectively, while the ac magnetization data revealed that the rare-earth (Ho) ordering occurs at similar to 8 K for HoCrO3 and Ho0.67Gd0.33CrO3 samples. Temperature-induced magnetization reversal and spin reorientation were observed in GdCrO3 bulk sample, which depends on applied magnetic field and disappears at similar to 1500 Oe and 500 Oe, respectively. By fitting the dc magnetic data with Curie-Weiss law, the effective magnetic moments were calculated to be 11.66 mu(B), 10.23 mu(B), and 9.90 mu(B) for the HoCrO3, Ho0.67Gd0.33CrO3, and GdCrO3 samples, respectively. The isothermal magnetization data showed that the magnetic behavior changed from canted antiferromagnetic in low temperature region (below Neel temperature) to paramagnetic at high temperature. It was found that Gd substitution considerably improves the magnetocaloric effect of HoCrO3. Pure GdCrO3 bulk sample showed giant magnetocaloric entropy change (31.6 J/kg K at temperature similar to 5 K and at similar to 70 kOe), which is higher than that for polycrystalline RMnO3, RCrO3, and RFeO3 bulk powder samples. This renders GdCrO3 useful for potential applications in low-temperature magnetic refrigeration. Published by AIP Publishing.