Computer Simulation of Magnetic Properties of Nanocomposite Magnets

Fukunaga, H.; Kitajima, N.; Kanai, Yasushi

doi:10.2320/matertrans1989.37.864

Cited by 29 publications

(7 citation statements)

References 12 publications

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“…We consider a magnetocrystalline anisotropy energy and Zeeman energy for each cell in which only one magnetization exists. The magnitude of anisotropy which is comparable to the value adopted by Fukunaga et al [9]. The exchange constant JHS (between Fe and Nd-Fe-B cells) have been adjusted to be 2.0xl0-3 J/m 2 so as to best reproduce the experimental data for mUltilayers [8].…”

Section: N Mrcromagnetic Calculation For Nanocomposite Magnetssupporting

confidence: 48%

Fabrication of Exchange-Coupled α-Fe/Nd-Fe-B Multilayer Thin-Film Magnets

et al. 1998

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Abstract---Multilayers having the form of TilFe/ [Nd-F e-BIF e ]x5ffi/glass were fabricated on glass substrates by means of rf sputtering and subsequent annealing. We have confirmed that these films keep clear multilayer structure and Nd2FelJ3 grains were randomly aligned. We have observed the spring-back behavior in the magnetization curves, which confirms the exchange coupling between Fe and Nd-Fe-B layers. Moreover, micromagnetic calculations applied for nanocomposite magnets have been performed, which indicated that good alignment of hard magnetic phase and crystal grain size less than 10 nm are extremely important factors to derive the potential for nanocomposite magnets. I . INTRODUCTIONNanocomposite magnets [l] are expected to have a potential for high performance magnetic powders for bonded magnets. The magnetic properties of nanocomposite magnets strongly depend on their nanostructures, so it is necessary to investigate the relation between magnetic properties and structures in detail. Nanocomposite magnets are obtained mainly by melt-spinning or rapid-quenching process[2], [3]. However, it is not easy to control the nanostructure by using such a method. As proposed by Skomski and Coey[4], a multilayered two phase magnet, consisting of alternating hard and soft magnetic layers has the advantage that individual layer thickness can be controlled precisely. AI-Omari and Sellmyer[5] found the exchange-coupled behavior in CoSmlFeCo bilayer films, while a remanence-enhancement behavior have been reported by Parhofer et al. [6] observed for Nd-FeBlFe/Nd-Fe-B trilayers. We have succeeded in fabricating exchange-coupled a-Fe/Nd-Fe-B multilayer films with Ti both for underlayers and overlayers, and reported the dependence of magnetic properties on layer thickness [7]. Moreover, we have estimated the coupling strength between a-Fe and Nd-Fe-B layers to be about 10% of the FelFe and Nd-Fe-B/Nd-Fe-B couplings by comparing the experiments with micromagnetic calculations [8]. In this paper, we will report the more advanced experimental and calculated results and discuss the directions of improvement for magnetic properties of nanocomposite magnets. All the films were annealed at 873 or 923 K for 30 minutes with the pressure below 4.0xlO-4 Pa to crvstallize the Nd2Fe14B phase. The magnetization curves were measured at room temperature by means of vibrating sample magnetometer with a maximum field of l.2 MAIm applied parallel to the film plane. X-ray diffractometer was used to study the structural properties of the films. The composition of the as-sputtered Nd-Fe-B films were determined by the EPMA. Transmission electron microscopy (TEM) images and Auger profiles were used to confirm the multilayer structure of annealed samples. Ill. EXPERIMENT AL RESULTS AND DISCUSSIONSAccording to the EPMA results, the composition ofthe as-sputtered Nd-Fe-B films were found to be Nd13-1SFebalB7-11, so the each Nd-Fe-B layer in a-Fe/NdFe-B muItilayer films is expected to be almost of single phase containing NdzFel4B grains. We have co...

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Section: N Mrcromagnetic Calculation For Nanocomposite Magnetssupporting

confidence: 48%

Fabrication of Exchange-Coupled α-Fe/Nd-Fe-B Multilayer Thin-Film Magnets

et al. 1998

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“…According to theoretical investigations [4,5], the grain size of the magnetically softer component in a nanocomposite magnet must be around 10 nm so that the magnetic moments of this component can have a strong intergranular exchange coupling with the hard magnetic component, for instance, Nd 2 Fe 14 B. In such a structure, magnetization vectors in the soft magnetic phase are effectively locked to prevent unfavourable rotation of magnetization from occurring.…”

Section: Nanocomposite Permanent Magnet Structurementioning

confidence: 99%

Nd-Fe-B nanocomposite permanent magnets

Hirosawa¹

2004

Series in Material Science and Engineering

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“…Based on numerical calculations, the achievable (BH) max for NdFeB based magnets were estimated to be about 400 kJ/m 3 whereas the experimentally measured value has not exceeded 160 kJ/m 3 [47,48]. This difference may be caused by the suppression of nonuniform magnetization reversal [49]. For nanocomposites Nd 2 FeHB/a-Fe, Fe 3 B, Fe 2 3B 6 increasing Fe3b content improves the coercive field, but reduces the remanence and deteriorates the sequence of the hysteresis loop [17].…”

Section: Exchange-coupled Nanocrystalline Magnetsmentioning

confidence: 99%

DEVELOPMENT OF HIGH PERFORMANCE PERMANENT MAGNETS BASED ON Nd-Fe-B SYSTEM

Pourarian

2000

Magnetic and Superconducting Materials

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Rare earth iron boron magnets based on Nd 2 Fei.iB type is the most powerful permanent magnets, which have outstanding magnetic properties in the vicinity of room temperature. Production of NdFeB is carried out by two distinctly different processes. These include the conventional powder -sintering process and consolidation of rapidly solidified powders. The latter is used to produce both bonded and anisotropic bulk magnets. NdFeB sintered magnets essentially consist of three basic phases; Nd 2 FeuB (), Nd|Fe 4 B4 phase (n.) and Nd-rich phase (n) Therefore, the magnetic properties of the magnets strongly depend on their microstructure. The current focus of NdFeB magnet research and development is on improvement of the magnetic properties such as the magnetic remanence (B r ) and intrinsic coercivity (He,), corrosion resistance and temperature characteristics of sintered magnets and rapidly solidified (melt spinning) magnets. Since the discovery of NdFeB magnets, their performance has been continuously enhanced and the current maximum energy product is achieved to be 444 ld/m 3 (55.8 MGOe). Other processes also have been used for improving microstructure for developing high energy product NdFeB magnets. These processes include: i) mechanical alloying process of metals which uses an inter-diffusional reaction magnet, ii) HDDR process (hydrogenation, disprorportionation, desorption, recombination) of magnet powder, and iii) nanocrystalline composite magnet (exchange-coupled) which are composed of magnetically hard and soft grains The negative side of the NdFeB magnet is their low corrosion resistance They are sensitive to attack by both climatic and corrosive environments, resulting in deterioration of the hard magnetic properties of the magnet In this paper the development of the high-energy product NdFeB based magnets in terms of improved microstructure and magnet processing methods is reviewed.

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Computer Simulation of Magnetic Properties of Nanocomposite Magnets

Cited by 29 publications

References 12 publications

Fabrication of Exchange-Coupled α-Fe/Nd-Fe-B Multilayer Thin-Film Magnets

Fabrication of Exchange-Coupled α-Fe/Nd-Fe-B Multilayer Thin-Film Magnets

Nd-Fe-B nanocomposite permanent magnets

DEVELOPMENT OF HIGH PERFORMANCE PERMANENT MAGNETS BASED ON Nd-Fe-B SYSTEM

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Computer Simulation of Magnetic Properties of Nanocomposite Magnets

Cited by 29 publications

References 12 publications

Fabrication of Exchange-Coupled &alpha;-Fe/Nd-Fe-B Multilayer Thin-Film Magnets

Fabrication of Exchange-Coupled &alpha;-Fe/Nd-Fe-B Multilayer Thin-Film Magnets

Nd-Fe-B nanocomposite permanent magnets

DEVELOPMENT OF HIGH PERFORMANCE PERMANENT MAGNETS BASED ON Nd-Fe-B SYSTEM

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Fabrication of Exchange-Coupled α-Fe/Nd-Fe-B Multilayer Thin-Film Magnets

Fabrication of Exchange-Coupled α-Fe/Nd-Fe-B Multilayer Thin-Film Magnets