Microstructure, magnetocaloric effect and near tricritical mean-field critical behavior of La 0.67 Ca 0.33-x K x MnO 3 porous nanospheres prepared by solvothermal method

In this study, La 0.67 Ca 0.33-x K x MnO 3 porous nanospheres with K + replacing Ca 2 + were prepared by the solvothermal method. The microstructures, surface valence, magnetic properties, magnetocaloric effect and critical parameters of magnetic phase transition were investigated. The structural characterization showed that the grain size of La 0.67 Ca 0.33-x K x MnO 3 exhibited an increasing and then decreasing trend with the increase of K + doping. The magnetic testing of La 0.67 Ca 0.33-x K x MnO 3 revealed that K + doping increased the phase transition temperature of the system and modified the magnetic interactions before and after the phase transition temperature. As a result, the critical behavior of the magnetic phase transition was affected with K + doping. When x = 0.05 and 0.1, the critical behavior of samples exhibited similarities to the tricritical mean-field model. Furthermore, K + doping enhanced the magnetic refrigeration ability of the system, with the maximum magnetic entropy reaching 5.99 J/kg K for K-0.05.