Preparation And First-principles Study Of Ion Doped M-type Strontium Ferrite

M-type strontium ferrite is a kind of high-performance permanent magnetic material.Because M-type ferrite has a high coercive force and uniaxial magnetocrystalline anisotropy,good chemical stability and low cost,it can be used in many fields such as aerospace,national defense,industrial manufacturing and electronic devices.With the improvement of the quality of life and the rapid development of industries and national defense,the demand for M-type strontium-barium ferrite increases,and performance requirements become higher and higher.Therefore,researchers have continuously improved its magnetic properties in terms of its preparation methods,process parameters,and new formulations.In recent years,the method of rare earth ion doping has become a hot topic in this field.In this paper,sol-gel self-combustion and chemical co-precipitation methods are mainly used to prepare M-type strontium ferrites with equivalently substituted Sm-Ni and Gd-Ni.X-ray diffractometer?XRD?,scanning electron microscope?SEM?,vibration sample magnetometer?VSM?,and infrared spectrometer?IR?were used to analyze the phase composition,micromorphology,and magnetic properties.Mat Studio is used for modeling and VASP is used for first principles calculation.The stable structure is calculated by optimization,and then the electronic structure characteristics and magnetic properties were calculated after static self-consistency,The experimental and calculation results are as follows:1. Sr_1-x?Sm/Gd?_xFe_12-xNi_xO₁₉?x=0,0.05,0.1,0.15,0.2?was prepared by chemical co-precipitation.Doped with Sm-Ni:When 0?x<0.2,it is a single M-type strontium ferrite.When x=0.2,the impurity phases Fe₂O₃ and Sm Fe O₃ appear.The grain shape is approximately hexagonal,and the size is about 80-150 nm.When x=0.15,the saturation magnetization Ms and the residual magnetization Mr reach a maximum of 43 emu/g and 27.06 emu/g respectively.When x=0,the coercive force Hc is a maximum of 6452 Oe,and decreases as the doping amount increases.Doped with Sm-Ni:When 0?x<0.15,it is a single M-type strontium ferrite.When x=0.15,impurity phases Fe₂O₃and Gd Fe O₃ appear.The grain shape is approximately hexagonal,and the size is about 80-150 nm.At x=0.1,the saturation magnetization Ms and the residual magnetization Mr reach a maximum of 41.04 emu/g and24.73 emu/g.When x=0,the coercive force Hc is a maximum of 6452 Oe and decreases with increasing doping.2. Sr_1-x?Sm/Gd?_xFe_12-xNi_xO₁₉?x=0,0.05,0.1,0.15,0.2?prepared by sol-gel and self-combustion method.Doped with Sm-Ni:When 0?x<0.1,it is a single M-type hexaferrite.When x=0.1,impurity phase Fe₂O₃ appears.The grain shape is a sheet hexagon,part of which is irregular,and size about 120-200 nm.When x=0.05,the saturation magnetization Ms and the residual magnetization Mr reach a maximum of43.71 emu/g and 26.35 emu/g respectively.When x=0,the coercive force Hc is at a maximum of 6620 Oe,and decreases with increasing doping.Doped with Gd-Ni:When x=0,it is a single M-type hexaferrite phase.When x=0.05,the impurity phase Fe₂O₃ appears.The grain shape is sheet hexagon and irregular sheet,the size is about100-300 nm.When x=0.05,the saturation magnetization Ms and the residual magnetization Mr reach the maximum values of 46.26 emu/g and 28.74 emu/g respectively.When x=0,the coercive force Hc is a maximum of 6620 Oe,and decreases with increasing doping amount.3. The first principles based on density functional theory were used to calculate the M-type strontium ferrite,and the approximate method GGA+U was used to optimize the crystal structure and calculate the properties.The bandgap of Sr Fe₁₂O₁₉was calculated to be 1.681 e V,which was the semiconductor characteristic,and the total magnetic moment was 39.97?_B.The stable crystal structure of Sr_0.5Sm_0.5Fe_11.5Ni_0.5O₁₉ was calculated.Compared with the undoped,lattice constant is slightly reduced,the band gap was reduced to 0.543 e V and the valence band passes through the Fermi level,indicating that it has a doped P-type semiconductor characteristic.And the magnetic moment was reduced to 38.37?_B.