Spin reorientation, magnetocaloric effect and metamagnetic transitions in 50% Mn substituted RFeO₃ (R = Eu, Ho and Er)

The magnetic and magnetocaloric properties of rare earth orthoferrites are studied with 50% Mn substitution in the Fe site. Polycrystalline samples of RFe_0.5Mn_0.5O₃(R=Eu, Ho, Er) were synthesized and the crystal structure was resolved by Rietveld refinement of X-ray diffraction patterns. All samples exhibit a PM to AFM transition near room temperature as follows:T_N1(EuFe_0.5Mn_0.5O₃)~280K,T_N1(HoFe_0.5Mn_0.5O₃)~290K, T_N1(ErFe_0.5Mn_0.5O₃)~245K. As temperature decreases, all samples except HoFe_0.5Mn_0.5O₃ show a sudden drop in the magnetization which is similar to the spin reorientation (SR) observed in RFeO₃. As temperature further reduces below SR, ErFe_0.5Mn_0.5O₃ shows magnetization reversal for FCW curves taken in fields less than 50 Oe. Both Er and Ho based samples show high isothermal magnetic entropy change values of -ΔS_M= 13.4 J/Kg.K (ErFe_0.5Mn_0.5O₃, at ~9.5 K, ΔH = 7 T) and -ΔS_M=11.9 J/Kg.K (HoFe_0.5Mn_0.5O₃, at ~9.5 K, ΔH = 7 T). EuFe_0.5Mn_0.5O₃ shows a metamagnetic transition at low temperatures. Our studies confirm that, by substituting 50% Mn in Fe site, T_N reduces and T_SR increases. High isothermal magnetic entropy change, room temperature T_N and T_SR make these interesting multifunctional materials.