LAUSR

Abstract We have investigated the magnetocaloric effects and critical behaviors of Eu2NiMnO6 and Dy2NiMnO6 double perovskite oxides. For a magnetic field varying from 0 to 7 T, the maximum values of the magnetic entropy change ( | Δ S M max | ) reach 4.0 J/kg K and 5.2 J/kg K, and the relative refrigeration capacity (RCP) values are 241.5 J/kg and 385.1 J/kg for Eu2NiMnO6 and Dy2NiMnO6, respectively. The relatively high values of | Δ S M | and RCP suggest that these double perovskite oxides can be used as candidates of magnetic refrigerants working in a wide temperature range. Various techniques such as modified Arrott plot, Kouvel-Fisher method and critical isotherm analysis are used to estimate the critical exponents (β, γ and δ) as well as TC for Eu2NiMnO6. These critical exponents not only obey the Widom scaling relation δ = 1 + γ / β , but also fulfill the scaling equation M ( H , e ) = e β f ± ( H / e β + γ ) where e = (T – TC)/TC, f+ (T > TC) and f- (T