Multi-element doping system simulation method for regulating and controlling magnetic performance of rare earth strontium barium ferrite

Abstract

The invention discloses a multi-element doping system simulation method for regulating and controlling the magnetic performance of rare earth strontium-barium ferrite. The method comprises the following steps: S1, establishing a strontium-barium mixed ferrite permanent magnet material BSCF theoretical model doped with different rare earth elements based on material calculation software Materials Studio Visualization; s2, on the basis of a density functional theory (DFT) framework, VASP software is used for carrying out first principle calculation and analysis on the BSCF theoretical model, so that the magnetic performance change relation of the BSCF under different rare earth metal elements and different doping proportions is obtained; the method comprises the steps of S1, establishing a BSCF theoretical model, S2, establishing a BSCF theoretical model, S3, presetting different types of rare earth metal elements and proportions for the BSCF ferrite permanent magnet material with predetermined magnetism, and S4, establishing different BSCF doping models based on MS software on the basis of the BSCF theoretical model, and performing magnetic performance verification on each BSCF doping model to find a doping proportion closest to the predetermined magnetism. The invention discloses a multi-element doping system simulation method for regulating and controlling the magnetic performance of rare earth strontium barium ferrite, and aims to realize accurate regulation and control on the magnetism when a magnetic material is designed.

Description

Technical Field

[0001] The present invention relates to the field of material design simulation, and more specifically, to a multi-element doping system simulation method for regulating the magnetic properties of rare earth strontium barium ferrite. Background Art

[0002] Ba 0.5 Sr 0.5 Co 0.5 Fe 0.5 O3(BSCF) is a perovskite oxide with unique crystal structure and electrochemical properties. Its inherent oxygen defects and specific elemental composition make it perform well in solid oxide fuel cells and gas sensors, so it has a wide range of applications in energy conversion and catalysis. However, in its application, it is prone to phase change, microstructure coarsening occurs during brazing, it is difficult to maintain stable performance under long-term operation conditions, and the activity of low-temperature redox reaction needs to be improved. These are closely related to its microstructure and magnetism. Fortunately, doping has been proven to be an effective method to improve the specific properties of multiferroic materials. Yu-Hua, Hou et al. calculated the electronic structure and magnetic properties of CoFe1.875RE0.125O4 (RE=Nd, Eu and Gd) and found that with the increase of atomic number, the decrease of RE3+ ions leads to a decrease in lattice constant, and Eu and Gd doping increases the net magnetic moment. Zhang, Wenwen and others have effectively improved the oxygen reduction activity and performance of medium-temperature solid oxide fuel cells (SOFCs) by doping simple perovskite oxides with rare earth ions, and proposed a new idea for the design of perovskite cathode materials. 0.5 Fe 0.5 The research on the magnetic effects of rare earth doping on perovskite materials is still superficial, and more detailed and in-depth academic discussions are needed on how rare earth doping changes the electronic structure and magnetic interaction mechanism of the material. Summary of the invention

[0003] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0004] In order to achieve these purposes and other advantages of the present invention, a multi-element doping system simulation method for regulating the magnetic properties of rare earth strontium barium ferrite is provided, characterized in that it includes:

[0005] S1. Based on the material calculation software Materials Studio Visualize, the BSCF theoretical model of strontium-barium mixed ferrite permanent magnet materials doped with different rare earth elements was established;

[0006] S2. Based on the density functional theory (DFT) framework, the VASP software was used to perform first-principles calculations and analyses on the BSCF theoretical model to obtain the relationship between the magnetic properties of BSCF under different rare earth metal elements and different doping ratios;

[0007] S3. For the BSCF ferrite permanent magnet material with predetermined magnetic properties, based on the magnetic property variation relationship obtained in S2, different types of rare earth metal elements and their proportions are preset to construct multiple groups of simulation example proportions;

[0008] S4. For multiple groups of simulation example ratios preset in S3, different BSCF doping models are constructed based on the BSCF theoretical model using MS software. The magnetic performance of each BSCF doping model is verified to find the doping ratio closest to the predetermined magnetic properties, and the difference between the two is calculated. If the difference meets the requirements, the process is terminated, otherwise it returns to S3.

[0009] Preferably, in S1, it further includes: performing magnetic calculations on the BSCF theoretical model based on DFT in VASP.

[0010] Preferably, in S2, the magnetic property change relationship is obtained in a manner including:

[0011] S20. On the basis of the unchanged geometric structure of the unit cell, establish the doping model I with the same rare earth metal element and different proportions. In VASP software, based on the density functional theory DFT framework, calculate and analyze the doping model I by first principles.

[0012] S21. On the basis of the unchanged geometric structure of the unit cell, a doping model II with different rare earth metal elements and the same proportion is established. In the VASP software, based on the density functional theory DFT framework, the first principle calculation and analysis of the doping model I are performed;

[0013] The K-point grid of the first Brillouin zone of the doping model I and the doping model II is set to 3×3×3, the plane wave cutoff energy is set to 500 eV, and the Hellmann-Feynman force is required to converge to The energy converges to 1×10 -5 eV;

[0014] The calculations described refer to the generalized gradient approximation GGA+U method based on the electron density combined with the spin-polarized DFT+U method with on-site Coulomb corrections for the d orbitals of all transition metal atoms.

[0015] Preferably, the Coulomb correction values ​​for Re, Fe, and Co are set to 6 eV, 3.5 eV, and 3 eV, respectively.

[0016] Preferably, the analysis refers to the analysis of the magnetic moment change, electron migration, hybridization characteristics, and atomic model, system energy, unit cell parameters, and formation energy stability of BSCF after doping with different elements based on the results obtained from first-principles calculations using dynamic relaxation structural optimization.

[0017] Preferably, the magnetic property variation relationship refers to:

[0018] From the perspective of structural properties of doping, after comprehensive geometric optimization, the BSCF structure doped with rare earth metal elements shows a trend of volume reduction compared with the pure BSCF structure, and the degree of volume reduction caused by Sc and Lu doping is positively correlated with the atomic radius of the two doping elements;

[0019] From the perspective of doping formation energy, except for Eu and Yb elements, the doping formation energy of other rare earth metal elements in BSCF is negative, and they can spontaneously replace the Ba site in BSCF;

[0020] From the perspective of doped electronic structure, the influence of Ba and Sr elements on the main electronic structure is relatively weak. Rare earth metal doping can change the magnetic properties of BSCF by changing the spin symmetry of Fe and Co atoms. Among them, Ce, Sc, and La can significantly change the electronic structure of BSCF.

[0021] From the perspective of doped magnetic properties, when Ce is used as a dopant, the magnetic moment of Co atoms decreases slightly, and the magnetic moment of Fe atoms is in an upward state; when Eu and Yb are used as dopants, the total magnetic moment decreases slightly; and when Sc, Y, La, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, and Tm are used as dopants, the doping of Co atoms causes the magnetic moment of the system to decrease; the effect of the number of doped atoms on the magnetic moment of BSCF atoms is correlated with different types of doped atoms.

[0022] The present invention includes at least the following beneficial effects: by obtaining the relationship between the changes in the magnetic properties of rare earth metal elements, the present invention derives the theory that different doping elements can regulate the magnetism of BSCF, and changing the number of doping atoms can also linearly regulate the magnetism. In practical applications, the magnetism of the material can be regulated by adjusting the doping atoms and the number of atoms, and excellent new materials with predetermined magnetic properties can be developed.

[0023] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1To study the structural properties and formation energy of rare earth element doped Ba1-xSrxCo1-yFeyO3, the atomic model used in the calculation is as follows: (a) the initial structure is Ba 0.5 Sr 0.5 Co 0.5 Fe 0.5 Atomic model of O3, (b) Ba is doped with Re atoms instead of Ba sites 0.375 Re 0.125 Sr 0.5 Co 0.5 Fe 0.5 O3 structure model, (c) is the Ba doped with Re atoms instead of Sr sites 0.5 Sr 0.375 Re 0.125 Co 0.5 Fe 0.5 O3 structural model;

[0025] Figure 2 The formation energy of BSCF doped with different rare earth elements replacing Ba / Sr sites

[0026] Figure 3 Formation energy of BSCF doped with different numbers of La atoms replacing Ba / Sr sites

[0027] Figure 4 Formation energy of BSCF doped with different numbers of Ce atoms replacing Ba / Sr sites

[0028] Figure 5 For BaCo 0.5 Fe 0.5 Partial density of states diagram of O3;

[0029] Figure 6 For Ba 0.5 Sr 0.5 Co 0.5 Fe 0.5 Partial density of states diagram of O3;

[0030] Figure 7 SrCo 0.5 Fe 0.5 Partial density of states diagram of O3;

[0031] Figure 8 is the partial state density of BSCF structure doped with different numbers of Ce atoms;

[0032] Fig. 9 The partial state density of BSCF structure doped with different numbers of La atoms;

[0033] Fig.10 Schematic diagram of electron transfer after doping with different rare earth atoms;

[0034] Fig.11 Schematic diagram of the magnetic moment of each atom and the total magnetic moment in BSCF after doping with different rare earth atoms;

[0035] Fig.12 Schematic diagram of the total magnetic moment of BSCF doped with different numbers of La atoms;

[0036] Fig.13 Schematic diagram of the total magnetic moment of BSCF doped with different numbers of Ce atoms;

[0037] Fig.14 This is an atomic model after Ce doping replaces Ba site;

[0038] Fig.15 Atomic model after two Ce doping sites replaced Ba;

[0039] Fig.16 Atomic model after three Ce doping sites are replaced;

[0040] Fig.17 Atomic model after four Ce doping sites replaced Ba. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0042] In view of the lack of systematic research on the magnetic effects of rare earth element doping on BSCF, this paper uses DFT+U method to calculate and explore the effects of rare earth element doping on Ba 0.5 Sr 0.5 Co 0.5 Fe 0.5The influence of different rare earth elements on the magnetic properties of BSCF. The results show that the influence of different rare earth elements on the magnetic properties of BSCF is significantly different. Among them, the doping of Sc, Y, La, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm and other elements leads to a significant decrease in the magnetic moment of the system, and the total magnetic moment drops to about 22.5μB, which is mainly attributed to the decrease in the average magnetic moment of Co atoms. In contrast, the doping of Ce, Eu, Yb, Lu and other elements has a smaller effect on the total magnetic moment, which is mainly due to the less decrease in the magnetic moment of Co atoms and the slight increase in the magnetic moment of Fe atoms. It is worth noting that Ce, as the most easily doped element, not only changes the magnetism of BSCF, but also significantly improves the electronic conductivity of the system. In addition, it is found that the influence of the doping amount on the electronic structure and magnetism of BSCF is also different, which needs to be analyzed according to the specific situation. These research results provide a valuable reference for understanding the influence of rare earth elements on the magnetism of BSCF, which helps to guide material design to achieve precise regulation of the magnetism of materials.

[0043] The main contents of the multi-element doping system simulation method for regulating the magnetic properties of rare earth strontium barium ferrite of the present invention include: (1) using the first principles method to calculate theoretical properties such as magnetic moment. (2) using the density functional theory first principles formation energy, state density, ELF, Bader charge transfer, and magnetic moment calculation method to study the influence of element doping on system performance. (3) based on the results obtained from the first principles calculation, analyze the change of magnetic moment after doping, electron migration, and hybridization characteristics. (4) establishing different models to calculate the influence of pure doping on system performance when the unit cell geometry structure remains unchanged.

[0044] The main scheme of the multi-element doping system simulation method for regulating the magnetic properties of rare earth strontium barium ferrite of the present invention includes:

[0045] Materials Studio Visualizer (MS) was used to establish theoretical models of representative rare earth cobalt permanent magnet materials such as BSCF, and VASP was used to perform spin-polarized DFT (GGA+U) calculations on the magnetic properties of the model, such as the magnetic moment of a single atom, the total magnetic moment, and other properties.

[0046] Vienna Ab-initio Simulation Package (VASP) software was used to study the atomic model, system energy, unit cell parameters, formation energy stability and other issues of BSCF under different element doping based on density functional theory and dynamic relaxation structure optimization.

[0047] VASP is used to study the theoretical model of BSCF under different element doping, including information such as magnetic moment intensity, DOS, ELF, and Bayde charge transfer, so as to find a doping structure with controllable magnetic properties to adapt to different application environments.

[0048] Since various atoms generally only change their valence electrons in chemical reactions, and the inner electrons and the nucleus are a relatively stable entity, the inner electrons of each atom are generally not involved in the calculation. In the calculation of the present invention, the electron orbit of the Re atom involved in the calculation is 4f65s25p66s2, and the electron orbit of the cobalt atom is 3d54s2. It should be noted that the Re atom here is the abbreviation of rare earth metal elements, representing a group of atoms, not one, and the number of electrons in each atom is different.

[0049] There are four inequivalent Co sites in the BSCF crystal. In the Ba site, the first shell of Ba is bonded to 12 O atoms in a 12-coordinate geometry with a bond length of 2.77 angstroms, and the second shell is bonded to 4 Co and 4 Fe. Sr has a similar coordination environment to Ba, with Co and Fe elements respectively coordinating with 6 surrounding O atoms in an octahedral coordination.

[0050] The computing environment of the present invention is the National Supercomputing Center in Shenzhen (Shenzhen Cloud Computing Center), with a hardware configuration of 256 CPU cores and 800GB storage space. The software used for the calculation is Materials Studio + VASP. The above scheme aims to systematically explore the effects of rare earth element (Sc, Y, La, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm) doping on Ba 0.5 Sr 0.5 Co 0.5 Fe 0.5 O3 (BSCF) electronic structure, spin and orbital magnetism, including the influence of magnetic anisotropy. DFT calculation is an important method to study the ground state structure, electronic, magnetic and optical properties of materials. The DFT+U method can better describe the electronic correlation effects of rare earth element doped materials by introducing the in-situ Coulomb repulsion term U, thereby improving the calculation accuracy. By studying the spin and orbital moment contributions of rare earth atoms and the magnetocrystalline anisotropy of these compounds, the effects of the types and concentrations of rare earth elements on the electronic structure and magnetism of BSCF are compared and analyzed, which will provide new directions for the research and development of new functional materials in the future.

[0051] Embodiment 1:

[0052] Considering the difference in atomic radius, this example uses different rare earth elements Re to replace Ba sites and Sr sites respectively to study the structural properties and formation energy of rare earth element-doped Ba1-xSrxCo1-yFeyO3. 0.5 Sr 0.5 Co 0.5 Fe 0.5 The first-principles calculation study of O3 (abbreviated as Re-BSCF) was carried out based on the density functional theory (abbreviated as DFT) framework with the help of Vienna Ab-initio Simulation Package (abbreviated as VASP) software. In this study, the plane wave basis set is used to describe the interaction mechanism between electrons and ions through the projected augmented wave (PAW) potential. The generalized gradient approximation (abbreviated as GGA) of the electron density, specifically using the Perdew-Burke-Ernzerhof (abbreviated as PBE) function, is included in the calculation system as an exchange-correlation correction function. Ba 0.5 Sr 0.5 Co 0.5 Fe 0.5 The unit cell structure of O3 contains a total of 40 atoms. For the rare earth doped system, the K-point grid in the first Brillouin zone is set to 3×3×3. The plane wave cutoff energy is set to 500 eV to ensure the calculation accuracy. During the relaxation process of the system, the Hellmann-Feynman force is required to converge to The energy converges to 1×10 -5 eV to meet the calculation criteria. In order to further accurately describe the electronic structure of the d orbitals of transition metal atoms, this study adopted the GGA+U method proposed by Dudarev et al., combined with the spin-polarized DFT+U framework, and performed on-site Coulomb corrections on the d orbitals of all transition metal atoms. This correction simulates the U eff The role of Hubbard correction. Specifically, the Coulomb correction values ​​U of Re, Fe, and Co are eff =UJ is set to 6eV, 3.5eV and 3eV respectively. f ), the following formula was used:

[0053] Ef=E(Re substitutedBSCF)-E(PureBSCF)+μBa / Sr–μRe (1)

[0054] Here, “E” represents the calculated energy and “μ” represents the corresponding chemical potential.

[0055] The initial structure of this example is as follows Figure 1 The Ba shown in (a) 0.5 Sr 0.5Co 0.5 Fe 0.5 The atomic model of O3 is as follows Figure 1 As shown in (b) and (c), the doping operation of the rare earth metal element in this example is carried out at the Ba / Sr site, which is selected based on the fact that its atomic radius is close to that of the rare earth element (Re) and significantly larger than the radius of the Co / Fe atom. After geometric relaxation treatment, the structural optimization unit cell parameters of the pure phase and the rare earth element Re doped are listed in detail in Table 1 (relaxed structural parameters (a, b, c) and crystal system types of pure BSCF and Re doped BSCF).

[0056] In the study of Re-doped BSCF, it can be seen from the data in Table 1 that after comprehensive geometric optimization, almost all BSCF structures doped with rare earth elements show a trend of volume reduction compared with pure BSCF structures. It is worth noting that the degree of volume reduction caused by Sc and Lu doping shows a proportional relationship with the atomic radius of the two doping elements, that is, the volume reduction caused by doping with elements with smaller atomic radius is more significant.

[0057] Table 1

[0058]

[0059] Furthermore, in the doping formation energy (abbreviated as E f ) studied the doping of Re at the Ba / Sr site in BSCF, and the calculation method described in equation (1) was used to obtain the following results: Figure 2 As shown. It is observed that the doping formation energy of most rare earth elements in BSCF is negative, which indicates that these Re elements can spontaneously replace the Ba site in BSCF. Among them, the doping formation energy of Eu element is close to zero, while the doping formation energy of Yb element is positive, which shows that due to their unique physical and chemical properties, Eu and Yb elements are not easy to spontaneously replace Ba sites, and thus more difficult to dope into the BSCF structure. On the other hand, by calculating the doping formation energy of Re element at Sr site, the results show that, except for individual elements, the doping formation energy of other Re elements at Sr site is similar to that at Ba site. It is worth noting that La and Ce metals have the lowest negative doping formation energy compared with other Re elements, which strongly suggests that La and Ce can more easily undergo substitution reactions at Ba / Sr sites due to their extremely low energy barriers. In order to further explore the effect of the number of doping atoms on the formation energy, taking La and Ce, the two most easily doped elements, as examples, the formation energies of BSCF doped with different numbers of La / Ce atoms at Ba / Sr sites were calculated. The results are shown in Figure 3 and Figure 4As shown in the figure, multiple atomic doping of La and Ce both show high feasibility. Specifically, the formation energy of La element is more negative when doped with the third atom, which indicates that this structure may be more stable in practical applications. The formation energy of Ce element is more negative when doped with the second atom, indicating that it may be easier to achieve at this doping level. These findings provide an important theoretical basis for understanding the doping behavior of rare earth elements in BSCF.

[0060] Furthermore, in the study of the electronic structure of Re-doped BSCF, in order to further explore the specific effect of rare earth element Re doping on its electronic structure, the present invention uses the GGA+U method to calculate the partial density of states (PDOS) of different rare earth elements doped into the Ba site of the BSCF unit cell. The relevant results are as follows: Figure 5-Figure 7 In this figure, the zero point on the energy axis is defined as the Fermi level (abbreviated as E F ) and marked with a dotted line. According to the conventional definition, energy states below the Fermi level are considered occupied states (i.e., valence bands), while energy states above the Fermi level are considered unoccupied states (i.e., conduction bands). First, the density of states of BSCF structures with different Ba / Sr ratios was calculated to reveal the influence of Ba and Sr elements on the electronic structure of the material. The results show that the orbits of Ba and Sr elements mainly contribute to the conduction band part, which reflects the similarity of their properties and has a relatively weak influence on the main electronic structure. Further observation revealed that BaCo 0.5 Fe 0.5 O3 and SrCo 0.5 Fe 0.5 The state density distribution of O3 is almost the same, which shows that Ba and Sr elements have a weak influence on the orbital magnetism of Co and Fe elements. It is worth noting that the state density of Co and Fe elements in the valence state shows an asymmetric distribution of spin-up and spin-down, and the spin-up state density is obviously dominant, which fully demonstrates that the BSCF material has significant spin magnetic characteristics. When Ba and Sr are doped half each, it is observed that the state density distribution of Co has changed to a certain extent. This may indicate that the magnetic electronic structure of the material will be affected, which will further affect the overall performance of the BSCF material.

[0061] Considering that the effects of Ba and Sr elements on the BSCF state density are relatively weak, this study will focus on the effects of rare earth elements on the electronic structures of Co and Fe. Figure 8Partial density of states diagrams of a series of Re-doped BSCFs are shown in detail, aiming to reveal the specific effects of different Re-doping on the electronic structure of BSCFs. The results show that the density of states distribution of most Re-doped BSCFs is roughly consistent with that of the original BSCFs. However, it is worth noting that Re doping changes the density of states distribution of a part of the Fe element, especially in the energy range of -6 to -7eV, where the density of states shows a different degree of broadening. Specifically, in BSCFs doped with rare earth elements such as Sc, Y, La, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, and Tm, the density of states distribution of the Fe element in the -7eV energy range shows similar characteristics, which is significantly different from the density of states distribution of the Ba element. In BSCFs doped with elements such as Ce, Eu, Yb, and Lu, the density of states distribution of the Fe element is more acute, which is similar to the density of states distribution of the original BSCF structure. In addition, compared with the original BSCF, Re doping also leads to a significant increase in the area of ​​the electron density of states of the Co element with spin down, which forms coordination with the electron density of states with spin up, thereby reducing the number of isolated electrons. The change in spin symmetry may weaken the magnetism of BSCF. It is worth noting that Ce doping has less effect on the state density distribution of Co element than other Re elements, indicating that its spin characteristics are closer to the original BSCF. Analysis shows that Re doping may change the magnetism of BSCF by changing the spin symmetry of Fe and Co atoms. In addition, the three elements Ce, Sc, and La also show additional state density contributions in the state density diagram. In particular, the Ce element contributes a significant peak near the state density, which will further change the electronic structure of BSCF, increase its electronic conductivity, and thus affect its physical and chemical properties. In contrast, the contribution of other rare earth elements in the state density distribution is almost negligible, and their effect on the electronic properties of BSCF is relatively weak.

[0062] In view of the relatively weak effects of Ba and Sr on the density of states of BSCF, this study will focus on the effects of rare earth elements on the electronic structure of Co and Fe. By comparing the partial density of states of a series of Re-doped BSCFs, the specific effects of different Re-doping on the electronic structure of BSCFs are revealed. The results show that the density of states distribution of most Re-doped BSCFs is roughly consistent with the density of states distribution of the original BSCF. However, it is worth noting that Re doping changes the density of states distribution of some Fe elements, especially in the energy range of -6 to -7eV, where the density of states shows different degrees of broadening. Specifically, in BSCFs doped with rare earth elements such as Sc, Y, La, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, and Tm, the density of states distribution of Fe elements in the -7eV energy range shows similar characteristics, which is significantly different from the density of states distribution of Ba elements. In BSCFs doped with Ce, Eu, Yb, and Lu, the density of states distribution of Fe elements is more sharp, which is similar to the density of states distribution of the original BSCF structure. In addition, compared with the original BSCF, Re doping also leads to a significant increase in the area of ​​the electron density of states of the Co element with spin down, which forms coordination with the electron density of states with spin up, thereby reducing the number of isolated electrons. The change in spin symmetry may weaken the magnetism of BSCF. It is worth noting that Ce doping has less effect on the state density distribution of Co element than other Re elements, indicating that its spin characteristics are closer to the original BSCF. Analysis shows that Re doping may change the magnetism of BSCF by changing the spin symmetry of Fe and Co atoms. In addition, the four elements Ce, Sc, La, and Gd also show additional state density contributions in the state density diagram. In particular, the Ce element contributes a significant peak near the state density, which will further change the electronic structure of BSCF, increase its electronic conductivity, and thus affect its physical and chemical properties. In contrast, the contribution of other rare earth elements in the state density distribution is almost negligible, and their effect on the electronic properties of BSCF is relatively weak.

[0063] In order to systematically verify the effect of the amount of doping elements on the electronic structure of BSCF, this study selected the most easily formed elements Ce and La as the research objects based on the previous formation energy calculation results, and calculated the state density distribution of BSCF under different amounts of Ce and La doping. Figure 8-Figure 9It can be seen that with the gradual increase in the number of Ce doping, the state density contribution of Ce element near the Fermi level shows a linear growth trend. This change not only significantly shortens the distance between the valence band and the conduction band, but also further enhances the electron transmission ability of the material. At the same time, 635AZ observed that the spin-up state density contribution of Co element in the valence band gradually decreases with the increase in the number of Ce atoms, and the asymmetric state density decreases, which will weaken the spin magnetism of the material to a certain extent. For the doping of La element, 635AZ found a similar law to that of Ce element. With the increase in the number of La atoms doped, its state density contribution in BSCF also increases. This change not only moves the overall state density center of the BSCF conduction band downward, but also further enhances the excitation and transmission ability of electrons. It is worth noting that although the asymmetry of Co element decreases slightly with the increase of La doping number, the spin-up state density peak of Fe element shows a significant growth trend. This may have an impact on the spin magnetism of the material.

[0064] From the electron localization function (ELF) images of the original BSCF system and the Ba site of the BSCF system doped with rare earth elements, it can be clearly observed that the initial Ba element exhibits a high degree of electron localization, while the doped Re element generally leads to a decrease in the degree of electron localization of the central atom, and significantly enhances the electron aggregation effect of the surrounding atoms. It should be noted that in the calculation process, the number of valence electrons corresponding to elements such as Ba, Sc, Y, La, Ce, Pr, Nd, Pm, and Sm is relatively large (Ce is equipped with 12 valence electrons, while other elements are 11), which leads to more obvious red features of the electron localization of these elements on the ELF image. In contrast, the electrons around atoms such as Sc, Y, Pr, Nd, Pm, and Sm appear yellow, which reflects that their degree of electron localization is lower than that of the Ba element, which means that these atoms have lost more electrons than Ba. In particular, the dark blue area appearing in the center of the Ce element can also confirm that the Ce atom has lost a large number of electrons during the doping process. On the other hand, the number of outer valence electrons calculated for elements such as Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu is relatively small (Eu and Yb each have 8 valence electrons, while other elements have 9). This results in their electron localization being significantly lower than that of elements such as Ba, making it difficult to clearly distinguish them in the ELF image. In order to quantify this difference more accurately, 635AZ further calculated the bader electron number, such as Fig.10As shown in the figure, from the calculation results of the bader electron number, it can be clearly seen that the number of lost electrons of elements such as Sc, Y, La, Ce, Pr, Nd, Pm, and Sm is significantly more than that of Ba, which is consistent with the results observed in the ELF image of 635AZ. In addition, the number of lost electrons of Eu and Yb is similar to that of Ba, which may indicate that they have certain similarities in electronic structure characteristics.

[0065] Furthermore, in the study of the magnetic properties of Re-doped BSCF, it was found that the introduction of Re dopants significantly changed the spin polarization state of Co and Fe elements in BSCF, thereby affecting the size of the material's magnetic moment. This change can be intuitively reflected by the asymmetry of the state density caused by Re doping in BSCF. In order to quantify the influence of rare earth elements, 635AZ plotted the total magnetic moment (abbreviated as Total), the average magnetic moment of Fe atoms (abbreviated as Fe) of BSCF under different Re dopants. average ) and the average magnetic moment of Co atoms (abbreviated as Co average ) changes, such as Fig.11 In the initial BSCF material, the total magnetic moment of 635AZ was observed to be at a relatively high level, with the atomic magnetic moment of Fe element being about 3.7μ B , and the atomic magnetic moment of Co is about 2.5μ B However, when Re is doped into BSCF, the total magnetic moment of the material generally shows a downward trend to varying degrees. Among them, the doping of rare earth elements such as Sc, Y, La, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, and Tm significantly reduces the magnetic moment of the system, and the average magnetic moment of Co element drops to 1.7μ B Around, the total magnetic moment drops to 22.5μ BAbout. This change is mainly attributed to the significant decrease in the magnetic moment of the Co element, which is consistent with the phenomenon observed by 635AZ in the density of states diagram (DOS) that the spin-down electronic state density of the Co element increases and the asymmetry decreases, resulting in a weakening of magnetism. In particular, when the Ce element is used as a dopant, 635AZ found that the magnetic moment of the Co atom decreases relatively little, while the magnetic moment of the Fe atom also increases slightly, which causes the total magnetic moment of the Ce-doped BSCF to remain at a high level similar to that of the original BSCF. This observation is consistent with the findings of 635AZ in the DOS analysis, further verifying the unique effect of Ce doping on the electronic structure and magnetism of BSCF. In addition, 635AZ also noticed that in the Eu-doped BSCF, although the magnetic moment of the Co element decreases more, the magnetic moment of the Fe element also increases significantly, which makes the decrease in its total magnetic moment relatively small. Similarly, the Yb-doped BSCF also shows the characteristic of less decrease in the total magnetic moment. These phenomena indicate that different Re dopants have significantly different effects on the magnetic moments of Co and Fe elements in BSCF, which in turn leads to diversified changes in the overall magnetic properties of the material.

[0066] In the study of the effect of the number of doping atoms on the magnetic moment of BSCF atoms, Figure 12-13 As shown, taking Ce and La as examples, 635AZ found that the effect of the number of doping atoms on the magnetic moment shows distinct differences due to the different types of atoms.

[0067] In order to explain the above problem more specifically, Figure 14-17 Taking the example of the present invention, the atomic model after different amounts of Ce doping replacing Ba sites is listed, and the influence of different atomic doping amounts of the same doping element on the magnetic properties of BSCF is analyzed. Specifically, in the original BSCF system, the total magnetic moment is as high as 28.7μB. Fig.14 As shown in Figure 1, when a Ce atom is introduced for doping, the total magnetic moment of the system decreases to 26.9 μB. As the number of Ce atoms doped increases, the total magnetic moment of the system shows a continuous downward trend. Fig.17 As shown in the figure, when 4 Ce atoms are doped, the total magnetic moment of the system drops significantly to 20.0 μB. This change is mainly attributed to the gradual decrease in the magnetic moment of Co atoms. As the number of Ce atoms increases, the magnetic moment of Co atoms shows a linear downward trend, which in turn leads to a corresponding decrease in the total magnetic moment of the system.

[0068] However, when La atoms were used for doping, 635AZ observed completely different results from Ce doping. When one La atom was doped, the total magnetic moment of the system decreased to 22.6μB. Interestingly, as the number of La doping increased further, the total magnetic moment of the system showed a slight upward trend, and the greater the number of doping, the greater the increase in the total magnetic moment. In particular, when 4 La atoms were doped, the total magnetic moment of the system increased to 24.0μB. These results fully demonstrate that the effect of the number of doping atoms on the magnetic moment of the BSCF system is significantly different, and different types of doping atoms will lead to completely different magnetic moment change trends.

[0069] This example uses the DFT+U method to systematically explore the effects of rare earth element doping on the electronic structure and magnetism of BSCF. The results show that the doping of different rare earth elements has significant and different effects on the magnetism of BSCF. Specifically, the doping of rare earth elements such as Sc, Y, La, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, and Tm leads to a significant decrease in the magnetic moment of the system, and the total magnetic moment is reduced to about 22.5μB. This change is mainly attributed to the significant reduction in the average magnetic moment of Co atoms. In contrast, the doping of elements such as Ce, Eu, Yb, and Lu has little effect on the total magnetic moment of the system, mainly because the reduction in the magnetic moment of Co atoms is small, and the magnetic moment of Fe atoms is slightly increased. It is worth noting that Ce, as one of the most easily doped rare earth elements, not only significantly changes the magnetic properties of BSCF, but also improves the electronic conductivity of the system. In addition, the study also found that the amount of doping also has different effects on the electronic structure and magnetism of BSCF, which further emphasizes that in practical applications, specific analysis should be carried out according to specific circumstances in order to fully understand and utilize the regulatory effect of doping atoms on the magnetism of materials. This study provides an important reference for understanding the influence of rare earth elements on the magnetism of BSCF, and also provides a theoretical basis for the development of new materials with excellent magnetic properties.

[0070] Example 2

[0071] It can be seen from Example 1 that the main contents of the relationship between the changes in magnetic properties caused by each rare earth metal element in the BSCF doping model include:

[0072] From the perspective of structural properties of doping, after comprehensive geometric optimization, the BSCF structure doped with rare earth metal elements shows a trend of volume reduction compared with the pure BSCF structure, and the degree of volume reduction caused by Sc and Lu doping is positively correlated with the atomic radius of the two doping elements;

[0073] From the perspective of doping formation energy, except for Eu and Yb elements, the doping formation energy of other rare earth metal elements in BSCF is negative, and they can spontaneously replace the Ba site in BSCF;

[0074] From the perspective of doped electronic structure, the influence of Ba and Sr elements on the main electronic structure is relatively weak. Rare earth metal doping can change the magnetic properties of BSCF by changing the spin symmetry of Fe and Co atoms. Among them, Ce, Sc, and La can significantly change the electronic structure of BSCF.

[0075] From the perspective of doping magnetic properties, when Ce element is used as dopant, the magnetic moment of Co atoms decreases slightly, and the magnetic moment of Fe atoms is in an upward state; when Eu and Yb elements are used as dopants, the total magnetic moment decreases slightly; and when Sc, Y, La, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, and Tm elements are used as dopants, the doping of Co atoms causes the magnetic moment of the system to decrease; the effect of the number of doping atoms on the magnetic moment of BSCF atoms is correlated with different types of doping atoms.

[0076] Based on the above-mentioned relationship between the changes in magnetic properties, we can preset different types of rare earth metal elements and proportions according to the magnetic requirements for BSCF magnetic materials in different application scenarios to construct multiple groups of simulation instance ratios, and then use MS software to construct different BSCF doping models based on the BSCF theoretical model for the preset multiple groups of simulation instance ratios, and then use VASP software for calculation and analysis, and verify the magnetic properties of each BSCF doping model to find the doping ratio closest to the predetermined magnetic properties, and calculate the difference between the two. If the difference meets the requirements, terminate the experiment, otherwise reset the ratio of the simulation instance and conduct a secondary simulation experiment until the magnetic properties of the BSCF doping model after calculation and analysis meet the requirements.

[0077] The above solution is only an illustration of a preferred embodiment, but is not limited thereto. When implementing the present invention, appropriate replacement and / or modification can be performed according to user needs.

[0078] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and the embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily realized. Therefore, without departing from the general concept defined by the claims and equivalent scope, the present invention is not limited to the specific details and the illustrations shown and described here.

Claims

1. A multi-element doping system simulation method for regulating the magnetic properties of rare earth strontium barium ferrite, characterized in that: include: S1. Based on the material calculation software Materials Studio Visualize, the BSCF theoretical model of strontium-barium mixed ferrite permanent magnet materials doped with different rare earth elements was established; S2. Based on the density functional theory (DFT) framework, the VASP software was used to perform first-principles calculations and analyses on the BSCF theoretical model to obtain the relationship between the magnetic properties of BSCF under different rare earth metal elements and different doping ratios; S3. For the BSCF ferrite permanent magnet material with predetermined magnetic properties, based on the magnetic property variation relationship obtained in S2, different types of rare earth metal elements and their proportions are preset to construct multiple groups of simulation example proportions; S4. For multiple groups of simulation example ratios preset in S3, different BSCF doping models are constructed based on the BSCF theoretical model using MS software. The magnetic performance of each BSCF doping model is verified to find the doping ratio closest to the predetermined magnetic properties, and the difference between the two is calculated. If the difference meets the requirements, the process is terminated, otherwise it returns to S3.

2. The multi-element doping system simulation method for regulating the magnetic properties of rare earth strontium barium ferrite according to claim 1, characterized in that: In S1, it also includes: magnetic calculations of the BSCF theoretical model based on DFT in VASP.

3. The multi-element doping system simulation method for regulating the magnetic properties of rare earth strontium barium ferrite according to claim 1, characterized in that: In S2, in S2, the magnetic property change relationship is obtained in a manner including: S20. On the basis of the unchanged geometric structure of the unit cell, establish the doping model I with the same rare earth metal element and different proportions. In VASP software, based on the density functional theory DFT framework, calculate and analyze the doping model I by first principles. S21. On the basis of the unchanged geometric structure of the unit cell, a doping model II with different rare earth metal elements and the same proportion is established. In the VASP software, based on the density functional theory DFT framework, the first principle calculation and analysis of the doping model I are performed; The K-point grid of the first Brillouin zone of the doping model I and the doping model II is set to 3×3×3, the plane wave cutoff energy is set to 500 eV, and the Hellmann-Feynman force is required to converge to The energy converges to 1×10 -5 eV; The calculations described refer to the generalized gradient approximation GGA+U method based on the electron density combined with the spin-polarized DFT+U method with on-site Coulomb corrections for the d orbitals of all transition metal atoms.

4. The multi-element doping system simulation method for regulating the magnetic properties of rare earth strontium barium ferrite according to claim 3, characterized in that: The Coulomb correction values ​​for Re, Fe, and Co were set to 6 eV, 3.5 eV, and 3 eV, respectively.

5. The multi-element doping system simulation method for regulating the magnetic properties of rare earth strontium barium ferrite according to claim 3, characterized in that: The analysis refers to the results obtained based on first-principles calculations, using dynamic relaxation structural optimization to analyze the changes in magnetic moments, electron migration, hybridization characteristics after doping with different elements, as well as the atomic model, system energy, unit cell parameters, and formation energy stability of BSCF.

6. The multi-element doping system simulation method for regulating the magnetic properties of rare earth strontium barium ferrite according to claim 1, characterized in that: The magnetic properties change relationship refers to: From the perspective of structural properties of doping, after comprehensive geometric optimization, the BSCF structure doped with rare earth metal elements shows a trend of volume reduction compared with the pure BSCF structure, and the degree of volume reduction caused by Sc and Lu doping is positively correlated with the atomic radius of the two doping elements; From the perspective of doping formation energy, except for Eu and Yb elements, the doping formation energy of other rare earth metal elements in BSCF is negative, and they can spontaneously replace the Ba site in BSCF; From the perspective of doped electronic structure, the influence of Ba and Sr elements on the main electronic structure is relatively weak. Rare earth metal doping can change the magnetic properties of BSCF by changing the spin symmetry of Fe and Co atoms. Among them, Ce, Sc, and La can significantly change the electronic structure of BSCF. From the perspective of doping magnetic properties, when Ce element is used as dopant, the magnetic moment of Co atoms decreases slightly, and the magnetic moment of Fe atoms is in an upward state; when Eu and Yb elements are used as dopants, the total magnetic moment decreases slightly; and when Sc, Y, La, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, and Tm elements are used as dopants, the doping of Co atoms causes the magnetic moment of the system to decrease; the effect of the number of doping atoms on the magnetic moment of BSCF atoms is correlated with different types of doping atoms.

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