Long-range ferromagnetic ordering in La0.7Sr0.3Mn0.9Cu0.1O3 manganite

Abstract

Nanosized La0.7Sr0.3Mn0.9Cu0.1O3 manganite was synthesized via the sol–gel procedures. The structural, morphological, magnetic and magnetocaloric properties as well as the critical phenomena were investigated. The sample was described by X-ray diffraction (XRD) technique at room temperature which confirms the single phase with a rhombohedral structure belonging to the R$$\overline{3}$$c space group. The magnetic measurements indicated the presence of a second-order ferromagnetic–paramagnetic phase transition at 320 K. According to hysteresis cycles, at 10 K a typical soft FM behavior with a low coercive field was observed. The critical exponents values (β, γ, and δ) as well as the Curie temperature TC were determined using different approaches such as the extrapolation of Arrott plots, Kouvel–Fisher (KF) method and critical isotherm analysis. The critical parameters values (β = 0.489 ± 0.003 with TC = 323.41 K ± 0.23, γ = 1.014 ± 0.020 with TC = 324.32 K ± 0.48 and δ = 3.074) are located near those theoretically predicted by mean-field theory, indicating the long-range ferromagnetic coupling in this system. The reliability of these critical parameters was confirmed by both the universal scaling hypothesis and the Widom scaling relation. Additionally, to estimate the spontaneous magnetization MS (T), we used a process which depends on the analysis of the magnetic entropy change (− ΔSM). A satisfactory agreement was found between the values of the spontaneous magnetization determined from the entropy change ((− ΔSM) vs. M2) and those obtained from the extrapolation of the Arrott curves (μ0H/M vs. M2).