Giant and highly anisotropic magnetocaloric effects in single crystals of disordered-perovskite RCr_0.5Fe_0.5O₃ (R= Gd, Er)

We have synthesized disordered-pervoskite RCr_0.5Fe_0.5O₃ (R=Gd, Er) single crystals and investigated the influences of magnetic anisotropy and additional ordering of rare-earth moments on the cryogenic magnetocaloric properties. Both GdCr_0.5Fe_0.5O₃ (GCFO) and ErCr_0.5Fe_0.5O₃ (ECFO) crystallize in an orthorhombic Pbnm structure with randomly distributed Cr³⁺ and Fe³⁺ ions. In GCFO, the long-range order of Gd³⁺ moments emerges at T_Gd = 11 K. The relatively isotropic nature of large Gd³⁺ moment originating from zero orbital angular moment exhibits giant and almost isotropic magnetocaloric effect with a maximum magneto entropy chagne as ΔS_M ~ 50.0 J/kgK. On the contrary, in ECFO, the Er³⁺ moments tend to align along the c-axis below T_Er = 12 K. The highly anisotropic magnetizations lead to a gaint rotating magnetocaloric effect demonstrated by a rotating magnetic entropy chagne ΔS_R = 21.8 J/kgK. Due to the disordered characteristic of Cr³⁺ and Fe³⁺ ions in these compounds, the magnetocaloric properties appear to be determined principally by the magnetic anisotropic of rare-earth magnetic moments.