Critical Behavior of Ni-doped La0.7Sr0.3MnO3 Ceramics

The effect of Ni substitution on the magnetic properties and the critical behavior of La0.7Sr0.3Mn1−xNixO3 compounds, which were prepared by the solid-state reaction method has been investigated. Based on our investigations of the temperature and the magnetic field dependences of magnetization M(T, H) data, it is shown that the Curie temperature (\( T_{\rm{C}}\)) of La0.7Sr0.3Mn1−xNixO3 compounds will be shifted toward room temperature with increasing Ni concentration (x), \(T_{\rm{C}}\) = 359–307 K for x = 0.0–0.1. By using the modified Arrott plots and the Kouvel–Fisher methods together with \(M(H,T)\) data in the vicinity of the ferromagnetic (FM)–paramagnetic phase transition, the critical exponents (β, γ, and δ) have been determined. Our results show the existence of a short-range FM order in the undoped sample (x = 0). The values of β, γ, and δ will be shifted gradually toward those of the mean-field theory when x increases, suggesting that the long-range FM order is favored in Ni-doped samples. The results calculated on the effective exponents of \(\beta_{\rm{eff}} (\varepsilon )\) and \(\gamma_{\rm{eff}} (\varepsilon )\) in the asymptotic region indicate the existence of a magnetic disorder in all the samples.