Spin-Glass-like State and Reversible Room-Temperature Magnetocaloric Effect in Double Distorted Perovskites...

The preparation, complex magnetic properties and room-temperature magnetocaloric effect in Nd(Cu_3-Mn)Mn₄O₁₂ with cation distribution (Nd³⁺)_A(Cu_3-^2+xMn³⁺)_A'(Mn₁₊³⁺Mn_3-⁴⁺)_BO₁₂^2- (x = 1 and 1.5) have been reported. Both compounds show a sharp paramagnetic-ferromagnetic (FM) transition at T_C of 300 and 280 K, respectively. The substitution of Cu by Mn at the A' site induces the emergence of a spin glass state below ≈63 K for x = 1 and ≈72 K for x = 1.5 compound. Another antiferromagnetic-like magnetic transition is also observed in both compounds at 23 and 28 K, respectively, which is discussed as the antiferromagnetic coupling between Nd³⁺ at the A' site and (Mn³⁺/Mn⁴⁺) at the B site. These two compounds exhibit room-temperature magnetocaloric effect. For a small field of 2 T, the maximum magnetic entropy changes -ΔS_M are 1.5 J/kg K at 300 K and 1.4 J/kg K at 280 K, respectively. Moreover, the -ΔS_M(T) curves show an asymmetric distribution, resulting in high refrigerant capacity values for both compounds. We further demonstrate the distinct roles of the A'- and B-site spins on the magnetic properties and the origin of the spin-glass-like state in double distorted perovskites Ln(Cu_3-Mn)Mn₄O₁₂ family of compounds.