Magnetic and Magnetocaloric Properties of SrRu_1−xFe_xO₃

Abstract

We have systematically investigated the crystalline and electronic structures, magnetic and magnetocaloric properties of polycrystalline SrRu_1−xFe_xO₃ (x = 0 and 0.1) samples fabricated by the solid-state reaction method. The X-ray diffraction analyses of the samples indicated single phase orthorhombic perovskite structure. A thorough analysis of X-ray-absorption-based electronic structure revealed that both Fe²⁺ and Fe³⁺ ions are present in x = 0.1, in which concentration of Fe³⁺ ions is higher than that of Fe²⁺ ions. More careful analyses on the isothermal magnetization data derived from the Banerjee’s criterion demonstrated that the ferromagnetic-paramagnetic phase transition in all samples belongs to the second-order phase transition type. These results were also confirmed by a recently proposed quantitative criterion, which considered an exponent n from the magnetic field and temperature dependences of the magnetic entropy change (ΔS_m). Especially, around T_C, we have found that the ΔS_m reaches the maximum values of 1.65 and 1.32 J.kg⁻¹.K⁻¹ for x = 0 and 0.1, respectively, for a field change of ΔH = 50 kOe. Magnetic-field dependences of the maximum magnetic-entropy change (ΔS_max) obey a power law of ΔS_max(H) ∝ Hⁿ, where the values of n = 0.92–0.94 are far from the mean-field-theory value (2/3), indicating short-range magnetic order existing in the samples.

Fig. 4 (a), (b) M(H) data, (c), (d) Arrott plots of M² vs. H/M, and (e), (f) −ΔS_m(T) curves at various ΔH values for SrRu_1−xFe_xO₃. Arrow lines indicate the direction of increasing H value.