LAUSR

Abstract The structural and critical exponent analysis along with the universal behavior of the magnetocaloric effect in nano-crystalline La0.7Ca0.3Mn1−xNixO3 (x = 0.0, 0.02, 0.07, 0.10), manganites, exhibiting second order phase transition, are experimentally studied. Structural study using Rietveld refinement of X-ray diffraction patterns shows orthorhombic structure with Pnma space group. The Curie temperature could be tuned over a wide temperature range upon variation in the Ni2+ content. The nature of the transition was found to be of second order for all Ni2+-concentrations. Various techniques such as modified Arrott plots, Kouvel-Fisher method and critical isotherm were used to analyze the magnetic-field dependence of magnetization. Although the critical exponents beta (β), gamma (γ) and delta (δ) were analyzed with various theoretical models such as 3D-Ising model and 3D-Heisenberg model, the estimated critical exponents, obtained for different values of X, seemed to be consistent with those predicted by the mean-field theory. The critical exponents were further confirmed using the single scaling equation M(H,e) = eβf ± (H/eγ+β). The achieved results indicated that the obtained values of the critical exponents were reliable and reasonably accurate.