Magnetic Evolution Of Rare Earth Element Doping On A-cationic Of Double Perovskite Sr₂FeMoO₆

Perovskite manganese oxide room temperature magnetic refrigeration materials have attracted much attention due to their excellent physical properties,simple preparation,stable structure and low price.Starting with the properties and structure of double perovskite oxide SFMO,this paper introduces the research and development of SFMO as a magnetic refrigeration material.The influence of different doping at A site of SFMO on Curie temperature and magnetic entropy of SFMO is mainly introduced.The main research work is as follows:Double perovskite oxide Sr_2-xNd_xFeMoO6?SNFMO?was prepared by sol-gel method,and the effect of Nd doping on the properties of SFMO was studied.The Magnetocaloric Properties of SNFMO were calculated by magnetic data measured by VSM,and the changes of the Magnetocaloric Properties of SNFMO were analyzed.The following measurements were made:the phase structure of the samples at room temperature was determined by XRD and D8-DISCOVER X-ray powder diffractometer.The X-ray powder diffraction?XRD?data were analyzed by using structural analysis system?GSAS?.Hysteresis and Magnetocaloric curves of these compounds were measured by a vibration sampling magnetometer?Versalab,Quantum Design,USA?.The ionization valence in SNFMO was measured by X-ray photoelectron spectroscopy.Double perovskite oxide Sr_2-x-x Dy_xFeMoO₆ was prepared by solid-state reaction method.The A site of SFMO was doped by Dy.The XRD spectra of the samples were determined by X-ray powder diffractometer.The M-H and M-T curves of SDFMO were determined by vibration sampling magnetometer.Curie temperature and magnetic entropy of SDFMO were measured.The main results are as follows:The Curie temperature and magnetic moment of the sample decrease with the doping of Nd in double perovskite oxide Sr_2-xNd_x FeMoO₆.The M-T curves under different magnetic fields show that the blocking temperature of frozen particles decreases with the increase of external magnetic fields.XRD measurements of all Sr_2-xDy_xFeMoO₆ samples show that the order of samples decreases with the increase of Dy doping.The Magnetocaloric Properties of the samples were measured by VSM,and the FC and isothermal magnetization curves of Sr_2-x-x Dy_xFeMoO6 were measured.The FC curve of Sr_2-xDy_xFeMoO6 shows that the magnetization decreases with the doping of Dy.Sr_2-xDy_xFeMoO6?x=0.01,0.03,0.05?undergoes a transition between paramagnetism and ferromagnetism near Curie temperature.When the temperature is lower than Curie temperature,Sr_2-xDy_xFeMoO6 is ferromagnetic.When the temperature is higher than Curie temperature,Sr_2-xDy_xFeMoO6 is paramagnetic.