Effects of Ni Substitutions on the Critical Behaviors in $N{d}_{0.6}S{r}_{0.4}M{n}_{1-x}N{i}_x{O}_3$ Manganite

We investigate the effect of Ni$\text{-}$substitution on the crystalline structure and the critical behavior of $N{d}_{0.6}S{r}_{0.4}M{n}_{1-x}N{i}_x{O}_3$ (0.00 $\le$ x $\le$ 0.20) perovskite. X$\text{-}$ray diffraction patterns revealed that the major phase in all samples is the orthorhombic structure with space group $\mathit{\text{Pnma}}$. 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)phasetransition\mathrm{.}Theobtainedcriticalexponents($\beta$,$\gamma$and$\delta$)revealedthattheNi${\text -}$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.