Critical behavior and magnetocaloric effect in ferromagnetic nano-crystalline Pr₂CoMnO₆

To understand the nature of magnetic phase transition in nano-crystalline Pr$_2$CoMnO$_6$, in present study we have investigated the critical behavior and magnetocaloric effect. To estimate the critical exponents, various methods have been adopted like; the modified Arrott plots (MAP), the Kouvel-Fisher method (KF) and the critical isotherm analysis. This material shows a second order type a paramagnetic (PM) to ferromagnetic (FM) phase transition around 160 K. The critical exponents obtained from modified Arrott plots are $\beta$ = 0.531, $\gamma$ = 0.935 and $T_c$ = 160 K. Kouvel-Fisher method gives the exponents as $\beta$ = 0.533$\pm$0.001 with $T_c$ = 160.72$\pm$0.03 K and $\gamma$ = 0.932$\pm$0.003 with $T_c$ = 160.15$\pm$0.05 K. The third exponent $\delta$ = 2.763$\pm$0.005 obtained from critical isothermal is in agreement with Wisdom scaling rule. The estimated critical exponents do not exactly match with any established universality class, however, the deduced exponent values suggest that spin interaction in the present material is close to mean-field model which suggests the existence of long-range ferromagnetic order in nano-crystalline Pr$_2$CoMnO$_6$. The reliability of critical exponents is checked by universal scaling hypothesis on magnetic data across T$_c$. We have calculated the magnetic entropy change from magnetic data and found maximum value of -$\Delta$S = 2.05 (J kg$^{-1}$ K$^{-1}$) for 50 kOe at 180 K. Moreover, field dependent change in magnetic entropy obeys scaling and also indicates that the magnetic interaction is close to mean-field type.