Simulation Calculation Of The Occupancy Ordering Behavior And Physical Properties In Mn-Zn Ferrite

As a typical kind of soft magnetic materials,spinel ferrites are widely used in mechanical and electronic industry.Their properties are closely related with cation distribution on the sublattice.Clarifying the ordering behaviors of elements in the sublattices,is not only an important theoretical issue,but also can provide the detail information required to model the crystal structure so as to predict the physical and mechanical properties and thus design an optimized composition further.In this paper,base on the thermodynamics principle,aiding with the end-member compounds,the sublattices model was employed and supported with the first-principles calculations,to study the ordering behavior of the elements,i.e.the cation distribution in the AB2O4 soft magnetic ferrites materials and the related physical and mechanical properties.Through the analysis of the fine structure of elements ordering behaviors,we also predicted the magnetic and elastic properties of ferrites,and compare the results with available literatures.The main conclusions were stated in the following:(1)The value of thermodynamic functions of the end-member compounds is the linchpin of the prediction of the ordering behaviors of the elements.In this paper,we apply the methods of GGA,the method of mixing the total energy of GGA+U and GGA,and Debye model to calculate the thermodynamic databases of end-member compounds.Base on the thermodynamic database,we predict the occupancy ordering behaviors of the elements in the Mn-Zn ferrites,Mn-Ni ferrites and Zn-Ni ferrites,establishing the method how to obtain the occupancy results,which best close to the experimental values.In the MnFe2O4,the structure belongs to a normal spinel,when the temperature T>750 K,the structure shows some invert,as the temperature rises,invert more.In the ZnFe2O4,the structure belongs to the normal spinel,when the temperature T>1 000 K,the structure shows some invert,as the temperature rises,invert more also.In the NiFe2O4,the structure belongs to the inverse spinel structure,which almost unchanged when heat treatment temperature increase.Then the relationship between the occupying behaviors and the composition,as well as the heat treatment temperature in the MnxZn1-XFe2O4,MnxNi1-xFe2Oa and ZnxNi1-Fe2O4(x = 0,0.25,0.5,0.75,1.0)composited system were established based on the theoretically predictions.Base on the mixed total energy of the GGA+U and GGA methods,we obtain all the enthalpy of formation of end-member compounds which close to the experimental data.Therefore,we believe that based on method,we can accurately calculate the enthalpies of formation of transition metal oxides,and then build reliable formation enthalpy database.Finally,we use the software Gibbs2 to calculate the effect of the temperature on the Gibbs free energy,in order to make a more accurate description of Gibbs free energy.However the calculation method and the hardware conditions yet to explore further.(2)Based on the site occupying results of cation,the physical properties of MnxNi1-xFe2O4 were predicted further.With the increases of Mn content,the total magnetic moment in the series of ferrites decreases gradually and then reverse to 5μB,when the compositon is MnFe2O4.All of the elastic constants in the series of ferrites satisfy the mechanical stability criteria,and the predicted elastic constants are in good agreement with results of the available literatures.With the increase of Mn content,the bulk moduli in the series of ferrites are almost the same,which means their compressibilities are alike.Besides,shear modulus and Young’s modulus in the series of ferrites increase firstly and then decrease.Except for MnFe2O4,all of the series of ferrites are brittle in nature.(3)Based on the occupancy results we research the physical properties of ZnxNi1-xFe2O4.The total magnetic moment in the series of ferrites increases firstly and then decreases.The elastic constants in the series of ferrites all satisfy these mechanical stability criteria,and the predicted elastic constants are also in good agreement with results of the published literatures.With the increase of Zn content,the bulk modulus in the series of ferrites is almost the same,and all of them are higher than the NiFe2O4,which has been improved greatly due to the addition of Zn atoms.Besides,shear modulus and Young’s modulus in the series of ferrites increase firstly and then decrease,which means that all of the series of ferrites are brittle.