Toward understanding the microstructure characteristics,phase selection and magnetic properties of laser additive manufactured Nd-Fe-B permanent magnets

Nd-Fe-B permanent magnets play a crucial role in energy conversion and electronic devices.The essential magnetic properties of Nd-Fe-B magnets,particularly coercivity and remanent magnetization,are significantly infuenced by the phase characteristics and microstructure.In this work,Nd-Fe-B magnets were manufactured using vacuum induction melting(VIM),laser directed energy deposition(LDED)and laser powder bed fusion(LPBF)technologies.Themicrostructure evolution and phase selection of Nd-Fe-B magnets were then clarified in detail.The results indicated that the solidification velocity(V)and cooling rate(R)are key factors in the phase selection.In terms of the VIM-casting Nd-Fe-B magnet,a large volume fraction of theα-Fe soft magnetic phase(39.7 vol.%)and Nd2Fe17Bxmetastable phase(34.7 vol.%)areformed due to the low R(2.3×10-1?C s-1),whereas only a minor fraction of the Nd2Fe14B hard magnetic phase(5.15 vol.%)is presented.For the LDED-processed Nd-Fe-B deposit,although the Nd2Fe14B hard magnetic phase also had a low value(3.4 vol.%)as the values of V(<10-2m s-1)and R(5.06×103?C s-1)increased,part of theα-Fe soft magnetic phase(31.7vol.%)is suppressed,and a higher volume of Nd2Fe17Bxmetastable phases(47.5 vol.%)areformed.As a result,both the VIM-casting and LDED-processed Nd-Fe-B deposits exhibited poor magnetic properties.In contrast,employing the high values of V(>10-2m s-1)and R(1.45×106?C s-1)in the LPBF process resulted in the substantial formation of the Nd2Fe14B hard magnetic phase(55.8 vol.%)directly from the liquid,while theα-Fe soft magnetic phase and Nd2Fe17Bxmetastable phase precipitation are suppressed in the LPBF-processed Nd-Fe-B magnet.Additionally,crystallographic texture analysis reveals that the LPBF-processedNd-Fe-B magnets exhibit isotropic magnetic characteristics.Consequently,the LPBF-processed Nd-Fe-B deposit,exhibiting a coercivity of 656 k A m-1,remanence of 0.79 T and maximum energy product of 71.5 k J m-3,achieved an acceptable magnetic performance,comparable to other additive manufacturing processed Nd-Fe-B magnets from MQP(Nd-lean)Nd-Fe-Bpowder.

Enhanced soft magnetic properties of SiO_(2)-coated FeSiCr magnetic powder cores by particle size effect

It has been known that metal FeSiCr powders with large average particle sizes have been typically employed to prepare magnetic powder cores(SMCs),with few studies reported on the influence of magnetic properties for original powders with various average particle sizes less than 10m.In this work,SiO_(2)-coated FeSiCr SMCs with different small particle sizes were synthesized using the sol-gel process.The contribution of SiO_(2)coating amount and voids to the soft magnetic properties was elaborated.The mechanism was revealed such that smaller particle sizes with less voids could be beneficial for reducing core loss in the SMCs.By optimizing the core structure,permeability and magnetic loss of 26 and 262 kW/cm^(3)at 100 kHz and 50 mT were achieved at a particle size of 4.8m and ethyl orthosilicate addition of 0.1 mL/g.The best DC stacking performance,reaching 87%,was observed at an ethyl orthosilicate addition rate of 0.25 mL/g under 100 Oe.Compared to other soft magnetic composites(SMCs),the FeSiCr/SiO_(2)SMCs exhibit significantly reduced magnetic loss.It further reduces the magnetic loss of the powder core,providing a new strategy for applications of SMCs at high frequencies.

First‑principles study on electronic structure,optical and magnetic properties of rare earth elements X(X=Sc,Y,La,Ce,Eu)doped with two‑dimensional GaSe

The electronic structure,magnetic,and optical properties of two-dimensional(2D)GaSe doped with rare earth elements X(X=Sc,Y,La,Ce,Eu)were calculated using the first-principles plane wave method based on den-sity functional theory.The results show that intrinsic 2D GaSe is a p-type nonmagnetic semiconductor with an indi-rect bandgap of 2.6611 eV.The spin-up and spin-down channels of Sc-,Y-,and La-doped 2D GaSe are symmetric,they are non-magnetic semiconductors.The magnetic moments of Ce-and Eu-doped 2D GaSe are 0.908μ_(B)and 7.163μ_(B),which are magnetic semiconductors.Impurity energy levels appear in both spin-up and spin-down chan-nels of Eu-doped 2D GaSe,which enhances the probability of electron transition.Compared with intrinsic 2D GaSe,the static dielectric constant of the doped 2D GaSe increases,and the polarization ability is strengthened.The ab-sorption spectrum of the doped 2D GaSe shifts in the low-energy direction,and the red-shift phenomenon occurs,which extends the absorption spectral range.The optical reflection coefficient of the doped 2D GaSe is improved in the low energy region,and the improvement of Eu-doped 2D GaSe is the most obvious.

Impact of Co^(2+)substitution on structure and magnetic properties of M-type strontium ferrite with different Fe/Sr ratios

Ion substitution has significantly improved the performance of ferrite magnets,and cobalt remains a key area of research.Studies on the mechanism of Co^(2+)in strontium ferrite,especially SrFe_(2n-x)Co_(x)O_(19-d)(n=6.1-5.4;x=0.05-0.20)synthesized using the ceramic method,showed that Co^(2+)preferentially enters the lattice as the Fe/Sr ratio decreases.This results in a decrease in the lattice constants a and c due to oxygen vacancies and iron ion deficiency.The impact of Co substitution on morphology is minor compared to the effect of the Fe/Sr ratio.As the Fe/Sr ratio decreases and the Co content increases,the saturation magnetization decreases.The magnetic anisotropy field exhibits a nonlinear change,generally increasing with higher Fe/Sr ratios and Co content.These changes in the performance of permanent magnets are attributed to the absence of Fe^(3+)ions at the 12k+2a and 2b sites and the substitution of Co^(2+)at the 2b site.This suggests that by adjusting the Fe/Sr ratio and appropriate Co substitution,the magnetic anisotropy field of M-type strontium ferrite can be effectively optimized.

Mechanical and magnetocaloric adjustable properties of Fe3O4/PET deformed nanoparticle film

The flexibility of nanoparticle films is a topic of rapidly growing interest in both scientific and engineering researches due to their numerous potential applications in a broad range of wearable electronics and biomedical devices.This article presents the elucidation of the properties of nanoparticle films.Here,a flexible film is fabricated based on polyethylene terephthalate(PET)and magnetic iron oxide at the nanoscale using layer-by-layer technology.The 2D thin flexible film material can be bent at different angles from 0°to 360°.With an increase in elastic deformation angles,the magnetocaloric effect of the film gradually increases in the alternating magnetic field.The test results from a vibrating sample magnetometer and a low-frequency impedance analyzer demonstrate that the film has a good magnetic response and anisotropy.The magnetocaloric effect and magnetic induction effect are controlled by deformation,providing a new idea for the application of elastic films.It combines the flexibility of the nanoparticle PET substrate and,in the future,it may be used for skin adhesion for administration and magnetic stimulation control.

Effect of In doping on the evolution of microstructure,magnetic properties and corrosion resistance of NdFeB magnets

The grain boundary phase affects the magnetic properties and corrosion resistance of sintered NdFeB magnets.In this work,a small amount of In was added to NdFeB magnets by induction melting to systematically investigate its effect on the evolution of the microstructure,magnetic properties and corrosion resistance of NdFeB magnets.Microstructural analysis illustrated that minor In addition generated more grain boundary phases and an abundant amorphous phase at the triple-junction grain boundary.While the addition of In failed to enhance the magnetic isolation effect between adjacent matrix grains,its incorporation fortuitously elevated the electrochemical potential of the In-containing magnets.Besides,during corrosion,an In-rich precipitate phase formed,hindering the ingress of the corrosive medium into the magnet.Consequently,this significantly bolstered the corrosion resistance of the sintered NdFeB magnets.The phase formation,magnetic properties and corrosion resistance of In-doped NdFeB magnets are detailed in this work,which provides new prospects for the preparation of high-performance sintered NdFeB magnets.

Structural Transformations and Multiferroic Properties of Bi_(1-x)Eu_(x)Fe_(0.95)Co_(0.05)O_(3)(x=0.05,0.10,0.15,and 0.20)

Bi_(1-x)Eu_(x)Fe_(0.95)Co_(0.05)O_(3 )(x=0.05,0.10,0.15,and 0.20) nanoparticles were prepared through the sol-gel technique.Its structure,local electronic structure,magnetic and electric properties were systematically investigated.X-ray diffraction data show(104),(110) bimodal alignment and high angular migration,indicating that with the increase of Eu substitution at Bi site,the structure of BFO undergoes a continuous change in crystal structure.The hysteresis loop and the FC/ZFC curve show how magnetism varies with the size of the field and temperature.Finally,the causes of magnetic changes were analyzed by studying SXAS and hysteresis loops.

Influences of divalent ion substitution on the magnetic and dielectric properties of W-type barium ferrite

Saturation magnetization,magneto-crystalline anisotropy field,and dielectric properties are closely related to microwave devices applied at different frequencies.For regulating the magnetic and dielectric properties of W-type barium ferrites,single-phase BaMe_(2)Fe_(16)O_(27)(Me=Fe,Mn,Zn,Ni,Co) with different Me ions were synthesized by the high-temperature solid-state method.The saturation magnetization(Ms) range from 47.77 emu/g to 95.34 emu/g and the magnetic anisotropy field(H_a) range from 10700.60 Oe(1 Oe=79.5775 A·m^(-1)) to 13739.57 Oe,depending on the type of cation substitution in the hexagonal lattice.The dielectric permittivity and dielectric loss decrease with increasing frequency of the AC electric field in the low-frequency region,while they almost remain constant in the high-frequency region.The charac teristics of easy regulation and preparation make it a potential candidate for use in microwave device applications.

Relationship between disorder,magnetism and band topology in Mn(Sb_(1-x)Bi_(x))_(2)Te_(4) single crystals

We investigate the evolution of magnetic properties as well as the content and distribution of Mn for Mn(Sb_(1-x)Bi_(x))_(2)Te_(4) single crystals grown by large-temperature-gradient chemical vapor transport method.It is found that the ferromagnetic MnSb_(2)Te_(4) changes to antiferromagnetism with Bi doping when x≥0.25.Further analysis implies that the occupations of Mn ions at Sb/Bi site Mn_(Sb/Bi) and Mn site Mn_(Mn) have a strong influence on the magnetic ground states of these systems.With the decrease of Mn_(Mn) increase of Mn_(Sb/Bi),the system will favor the ferromagnetic ground state.In addition,the rapid decrease of T_(C/N) with increasing Bi content when x ≤0.25 and the insensitivity of T_(N) to x when x> 0.25 suggest that the main magnetic interaction may change from the Ruderman-Kittel-Kasuya-Yosida type at low Bi doping region to the van-Vleck type in high Bi doped samples.

Effect of Y element on atomic structure, glass forming ability,and magnetic properties of FeBC alloy

The atomic structure of amorphous alloys plays a crucial role in determining both their glass-forming ability and magnetic properties. In this study, we investigate the influence of adding the Y element on the glass-forming ability and magnetic properties of Fe_(86-x)Y_xB_7C_7(x = 0, 5, 10 at.%) amorphous alloys via both experiments and ab initio molecular dynamics simulations. Furthermore, we explore the correlation between local atomic structures and properties. Our results demonstrate that an increased Y content in the alloys leads to a higher proportion of icosahedral clusters, which can potentially enhance both glass-forming ability and thermal stability. These findings have been experimentally validated. The analysis of the electron energy density and magnetic moment of the alloy reveals that the addition of Y leads to hybridization between Y-4d and Fe-3d orbitals, resulting in a reduction in ferromagnetic coupling between Fe atoms. This subsequently reduces the magnetic moment of Fe atoms as well as the total magnetic moment of the system, which is consistent with experimental results. The results could help understand the relationship between atomic structure and magnetic property,and providing valuable insights for enhancing the performance of metallic glasses in industrial applications.

Angular and planar transport properties of antiferromagnetic V_(5)S_(8)

Systemically angular and planar transport investigations are performed in layered antiferromagnetic(AF)V_(5)S_(8).In this AF system,obvious anomalous Hall effect(AHE)is observed with a large Hall angle of 0.1 compared to that in ferromagnetic(FM)system.It can persist to the temperatures above AF transition and exhibit strong angular field dependence.The phase diagram reveals various magnetic states by rotating the applied field.By analyzing the anisotropic transport behavior,magnon contributions are revealed and exhibit obvious angular dependence with a spin-flop vanishing line.The observed prominent planar Hall effect and anisotropic magnetoresisitivity exhibit two-fold systematical angular dependent oscillations.These behaviors are attributed to the scattering from spin–orbital coupling instead of nontrivial topological origin.Our results reveal anisotropic interactions of magnetism and electron in V5S8,suggesting potential opportunities for the AF spintronic sensor and devices.

Phase structure evolution and its effect on magnetic and mechanical properties of B-doped Sm_(2)Co_(17)-type magnets with high Fe content

The unique cellular microstructure of Fe-rich Sm_(2)Co_(17)-type permanent magnets is closely associated with the structure of the solid solution precursor.We investigate the phase structure,magnetic properties,and mechanical behavior of B-doped Sm_(2)Co_(17)-type magnets with high Fe content.The doped B atoms can diffuse into the interstitial vacancy,resulting in lattice expansion and promote the homogenization of the phase organizational structure during the solid solution treatment in theory.However,the resulting second phase plays a dominant role to result in more microtwin structures and highly ordered 2:17R phases in the solid solution stage,which inhibits the ordering transformation of 1:7H phase during aging and affects the generation of the cellular structure,and to result in a decrease in magnetic properties,yet the interface formed between it and the matrix phase hinders the movement of dislocations and enhances the mechanical properties.Hence,the precipitation of high flexural strain grain boundary phase induced by B element doping is also a new and effective way to improve the flexural strain of Sm_(2)Co_(17)-type magnets.Our study provides a new understanding of the phase structure evolution and its effect on the magnetic and mechanical properties of Sm_(2)Co_(17)-type magnets with high Fe content.

First-principles calculations of Ni–(Co)–Mn–Cu–Ti all-d-metal Heusler alloy on martensitic transformation,mechanical and magnetic properties

The martensitic transformation,mechanical,and magnetic properties of the Ni_(2)Mn_(1.5-x)Cu_(x)Ti_(0.5) (x=0.125,0.25,0.375,0.5) and Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5)[(x=0.125,y=0.125,0.25,0.375,0.5) and (x=0.125,0.25,0.375,y=0.625)]alloys were systematically studied by the first-principles calculations.For the formation energy,the martensite is smaller than the austenite,the Ni–(Co)–Mn–Cu–Ti alloys studied in this work can undergo martensitic transformation.The austenite and non-modulated (NM) martensite always present antiferromagnetic state in the Ni_(2)Mn_(1.5-x)Cu_(x)Ti_(0.5) and Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5) (y<0.625) alloys.When y=0.625 in the Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5) series,the austenite presents ferromagnetic state while the NM martensite shows antiferromagnetic state.Cu doping can decrease the thermal hysteresis and anisotropy of the Ni–(Co)–Mn–Ti alloy.Increasing Mn and decreasing Ti content can improve the shear resistance and normal stress resistance,but reduce the toughness in the Ni–Mn–Cu–Ti alloy.And the ductility of the Co–Cu co-doping alloy is inferior to that of the Ni–Mn–Cu–Ti and Ni–Co–Mn–Ti alloys.The electronic density of states was studied to reveal the essence of the mechanical and magnetic properties.

Low Temperature Heat Capacity of Zn Substituted Cobalt Ferrite Nanosphere:The Relation between Magnetic Properties and Microstructure

Co_((1-x))ZnxFe_(2)O_(4)nanospheres(x=0,0.5,0.8)with a unidirectional cubic spinel structure were prepared by a solvothermal method.By using a range of theoretical and empirical models,the experimental heat capacity values were fitted as a function of temperature over a suitable temperature range to explain the possible relationship between the magnetic properties and microstructure of the nanospheres.As a result,at a low temperature(T<10 K),the parameter Bfswdecreases with increasing Zn concentration,implying that the exchange interaction between A and B sites decreases.At a relatively high temperature(T>50 K),the Debye temperature decreases with increasing Zn concentration,which is due to the weakening of the interatomic bonding force after the addition of non-magnetic materials to the Co Fe_(2)O_(4)spinel ferrite.

Influence of Phosphorus Content and Magnetic Annealing on Soft Magnetic Properties of Electrodeposited Amorphous FeMnP Alloy Films

In this work, we investigated the influence of phosphorus and magnetic anneal on the soft magnetic properties of electrodeposited FeMnP alloy films prepared by changing sodium hypophosphite concentrations. X-ray diffraction radiation patterns showed an amorphous structure of electrodeposited alloy films. The saturation magnetization and coercivity value decreased from 586 emu/cc to 346 emu/cc, and 52 Oe to 18 Oe, with the P content increased, respectively. The absorption resonance peak became broad as the P content increased, and the natural resonance frequency decreased from 1.8 GHz to 0.6 GHz, with the P content increasing. Magnetic annealing of samples reduced the magnetic damping, and natural resonance frequency increased by about 1.8 GHz and 3.5 GHz for the sample with lower and higher P content. The film structure with lower P content changed at 300&#730;C, while the structure remains unchanged for the films with higher P content. Thus, the crystallization temperature could depend on the P content in the film. FeMnP alloy films could be used in high-frequency devices.

Synthesis, Characterization, and Effects of Morphology on the Magnetic Application Base Properties of Pure Nickel Oxide (NiO) and Cobalt-Doped Nickel Oxide/Nickel Hydroxide (CoxNi1-xO/Ni(OH)2) Nanocomposites

Nano particle (NP) morphology is one of the material properties at the origin of potential application base properties exploited in several engineering and technology domains, such as fuel cell, electrodes, catalysis, sensing, electric, thermal, magnetic, and photovoltaic applications. The general properties and particle morphology of nickel oxide/Nickel hydroxide NPs can be modified by the introduction of impurity atoms or ions. Nano sized nickel oxide/nickel hydroxide nanocomposites were obtained from the thermal decomposition of single molecular precursors synthesized by a modified oxalate route using Carambola fruit juice as a precipitating agent. The compositional and morphological variations were studied by introducing cobalt as an impurity ion at different w/w% fractions (0%, 0.1%, 0.3%, 0.5%, 1%, 3%, 5.0%, 40.0% and 50.0%) into the microstructure of the nickel oxide/hydroxide. The precursors were characterized by FT-IR, while TGA/DTG analysis was carried out to decompose the precursors. The precursors decomposed at 400°C and were characterized by PXRD and SEM/TEM. The results revealed that Pure Nickel Oxide (NiO) and, Cobalt-doped Nickel Oxide/nickel hydroxide (CoxNi1-xO/Ni(OH)2) Nano composites have been synthesized and the synthesized samples have exhibited three distinct morphologies (porous face-centered cubic nano rods, rough and discontinuous CoxNi1-xO/Ni(OH)2) composite and, smooth and continuous mix spherical/cuboidal mixed morphological phase of (NiO/CoO). The morphology of the NPs varied with the introduction of the dopant atoms and with increase in the concentration of dopant atoms in the composite. Magnetic studies using vibrating sample magnetometry revealed superparamagnetic properties which correlated strongly with particle size, shape and morphology. Observed values of retention (4.50 × 10-3 emu/g) and coercivity (65.321 Oe) were found for 0.5 w/w% corresponding to impregnated porous nanorods of Co-doped NiO, and retention (9.03 × 10-3 emu/g) and coercivity (64.341 Oe), for X = 50.0%, corresponding to an aggregate network of a Nano spherical/cubic CoO/NiO mixed phase. Magnetic properties within this range are known to improve the magnetic memory and hardness of the magnetic materials. Therefore, the synthesized Cobalt-doped Nickel Oxide/nickel hydroxide (CoxNi1-xO/Ni(OH)2) Nano composites have potential applications in Magnetic memories and hardness of magnetic materials.

Synthesis, Characterization, and Effects of Morphology on the Magnetic Application Base Properties of Pure Nickel Oxide (NiO) and Cobalt-Doped Nickel Oxide/Nickel Hydroxide (CoxNi1-xO/Ni(OH)2) Nanocomposites

Nano particle (NP) morphology is one of the material properties at the origin of potential application base properties exploited in several engineering and technology domains, such as fuel cell, electrodes, catalysis, sensing, electric, thermal, magnetic, and photovoltaic applications. The general properties and particle morphology of nickel oxide/Nickel hydroxide NPs can be modified by the introduction of impurity atoms or ions. Nano sized nickel oxide/nickel hydroxide nanocomposites were obtained from the thermal decomposition of single molecular precursors synthesized by a modified oxalate route using Carambola fruit juice as a precipitating agent. The compositional and morphological variations were studied by introducing cobalt as an impurity ion at different w/w% fractions (0%, 0.1%, 0.3%, 0.5%, 1%, 3%, 5.0%, 40.0% and 50.0%) into the microstructure of the nickel oxide/hydroxide. The precursors were characterized by FT-IR, while TGA/DTG analysis was carried out to decompose the precursors. The precursors decomposed at 400°C and were characterized by PXRD and SEM/TEM. The results revealed that Pure Nickel Oxide (NiO) and, Cobalt-doped Nickel Oxide/nickel hydroxide (CoxNi1-xO/Ni(OH)2) Nano composites have been synthesized and the synthesized samples have exhibited three distinct morphologies (porous face-centered cubic nano rods, rough and discontinuous CoxNi1-xO/Ni(OH)2) composite and, smooth and continuous mix spherical/cuboidal mixed morphological phase of (NiO/CoO). The morphology of the NPs varied with the introduction of the dopant atoms and with increase in the concentration of dopant atoms in the composite. Magnetic studies using vibrating sample magnetometry revealed superparamagnetic properties which correlated strongly with particle size, shape and morphology. Observed values of retention (4.50 × 10-3 emu/g) and coercivity (65.321 Oe) were found for 0.5 w/w% corresponding to impregnated porous nanorods of Co-doped NiO, and retention (9.03 × 10-3 emu/g) and coercivity (64.341 Oe), for X = 50.0%, corresponding to an aggregate network of a Nano spherical/cubic CoO/NiO mixed phase. Magnetic properties within this range are known to improve the magnetic memory and hardness of the magnetic materials. Therefore, the synthesized Cobalt-doped Nickel Oxide/nickel hydroxide (CoxNi1-xO/Ni(OH)2) Nano composites have potential applications in Magnetic memories and hardness of magnetic materials.

Effect of minor B addition on microstructure and properties of AlCoCrFeNi multi-compenent alloy

The influences of slight amount of B element on the microstructure and properties of AlCoCrFeNiBx high entropy alloys（x = 0,0.01,…,0.09 and 0.1,mole fraction） were investigated.The AlCoCrFeNi high entropy alloy exhibits equiaxed grain structures with obvious composition segregation.However,with the addition of B element,the alloys exhibit dendrite structures.Inside the dendrites,spinodal decomposition structure can be clearly observed.With the addition of B element,the crystal structures change from（B2 ＋ BCC） to（B2 ＋ BCC ＋ FCC） structures,and the hardness firstly increases from HV 486.7 to HV 502.4,then declines to HV 460.7（x ≥ 0.02）.The compressive fracture strength firstly shows a trend of increasing,and then declining（x ≥ 0.08）.The coercive forces and the specific saturation magnetizations of the alloys decrease as B addition contents increase,the decreasing coercive forces show a better soft magnetic behavior.

Microstructure and magnetic properties of anisotropic Nd-Fe-B magnets prepared by spark plasma sintering and hot deformation

Bulk anisotropic Nd-Fe-B magnets were prepared from hydrogen-disproportionation-desorption-recombination（HDDR） powders via spark plasma sintering（SPS） and subsequent hot deformation. The influence of sintering temperature on the structure and magnetic properties of the spark plasma sintered Nd-Fe-B magnets were studied. The remanence Br, intrinsic coercivity Hcj, and the maximum energy product（BH）max, of sintered Nd-Fe-B magnets first increase and then decrease with the increase of sintering temperature, TSPS, from 650 °C to 900 °C. The optimal magnetic properties can be obtained when TSPS is 800 °C. The Nd-Fe-B magnet sinter treated at 800 °C was subjected to further hot deformation. Compared with the starting HDDR powders or the SPS treated magnets, the hot-deformed magnets present more obvious anisotropy and possess much better magnetic properties due to the good c-axis texture formed in the deformation process. The anisotropic magnet deformed at 800 °C with 50% compression ratio has a microstructure consisting of well aligned and platelet-shaped Nd2Fe14 B grains without abnormal grain growth and exhibits excellent magnetic properties parallel to the pressing axis.

Microstructure and magnetic properties of Ni-Zn ferrites doped with MnO_2

To improve the performance of Ni-Zn ferrites for power field use,the influence of MnO2 additive on the properties of Ni-Zn ferrites was investigated by the conventional powder metallurgy.The results show that MnO2 does not form a visible second phase in the doping mass fraction range of（0-2.0%）.The average grain size,sintering density and real permeability gradually decrease with the increase of the MnO2 content.And the DC resistivity continuously increases with the increase of MnO2 content.The saturation magnetization（magnetic moment in unit mass） first increases slightly when mass fraction of MnO2 is less than 0.4% MnO2,and then gradually decreases with increasing the MnO2 mass fraction due to the exchange interaction of the cations.When the excitation frequency is less than 1 MHz,the power loss（Pcv） continuously increases with increasing the MnO2 content due to the decrease of average grain size.However,when the excitation frequency exceeds 1 MHz,eddy current loss gradually becomes the predominant contribution to Pcv.And the sample with a higher resistivity favors a lower Pcv,except for the sample with 2.0% MnO2.The sample without additive has the best Pcv when worked at frequencies less than 1 MHz;and the sample with 1.6% MnO2 additive has the best Pcv when worked at frequencies higher than 1 MHz.