| In recent years,with the constantly increasing need for powerful,clean,efficient,and miniaturized devices incorporating different physical properties,much attention has been attracted to double perovskite oxides as multifunctional materials because they simultane-ously possess magnetic,dielectric,magnetodielectric and magnetocaloric(MC)properties.La2NiMn06 is a typical one of them,the substitution of other rare-earth element on La will change some properties of double perovskite compounds.For example,Curie temperature shifts towards low temperature with decreasing lanthanide ionic radius,because the decrease of Ni2+-O-Mn4+ bond angle weakens the superexchnage interaction.Studies on structure,dielectric and magnetodielectric properties of Eu2NiMnO6 and Dy2NiMnO6 have revealed the application potentiality of this series of materials in spintronic devices.In the text we have investigated the magnetic properties and magnetocaloric effects of Eu2NiMnO6 and Dy2NiMnO6 double perovskite oxides,and the magnetic state of Eu2NiMnO6 in the vicinity of phase transition,that is,critical behavior.The main content are as follows:Firstly,the current research status of double perovskite manganese oxides is introduced,and the basic concepts,research status,and characterization methods of the magnetocaloric effect are briefly described.At the same time,the basic theory of critical behavior is ex-pressed.Secondly,we synthesize Eu2NiMnO6 and Dy2NiMnO6 polycrystalline oxides using the solid-state reaction method,and study their structure and magnetic properties.The test characterizations show that the magnetic entropy change and relative cooling capacity of the two samples are calculated by the isothermal magnetization curve,and it is found that there is a large entropy change value near the phase transition.Finally,in order to analyze the microscopic mechanism of the magnetocaloric effect near the phase transition,the critical behavior of Eu2NiMnO6 is analyzed and discussed in detail. |
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