We investigate the effect of Ni${ \text -}$substitution on the crystalline structure and the critical behavior of $Nd_{ 0.6}Sr_{ 0.4}Mn_{ 1-x}Ni_{ x}O_{ 3}$ (0.00 $\leq$ x $\leq$ 0.20) perovskite. X${ \text -}$ray diffraction patterns revealed that the major phase in all samples is the orthorhombic structure with space group $\textit{ Pnma}$. Rietveld refinement revealed a linear reduction in the lattice parameters along with monotonic reduction in the O2${ \text -}$Mn${ \text -}$O2 angel with increasing Ni concentration. The modified Arrott plots and the Kouvel${ \text -}$Fisher method have been used to analyze the magnetization isotherms near the paramagnetic to ferromagnetic (PM${ \text -}$FM) phase transition. The obtained critical exponents ($\beta$, $\gamma$ and $\delta$) revealed that the Ni${ \text -}$free sample is consistent with 3D${ \text -}$Heisenberg like behavior. However, upon Ni${ \text -}$substitution, the critical exponents exhibit a mean field like behavior. The reliability of the obtained critical exponent ($\beta$, $\gamma$ and $\delta$) values have been confirmed by the universal scaling behavior of the isothermal magnetization near the transition temperature.
Categories: cond-mat.str-el cond-mat.mtrl-sci