LaCo-substituted ferrite magnets, a new class of high-grade ceramic magnets; intrinsic and microstructural aspects

Kools, F.; Morel, A.; Größinger, R.; Breton, J.M. Le; Tenaud, P.

doi:10.1016/s0304-8853(01)00988-x

Cited by 192 publications

(93 citation statements)

References 6 publications

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“…The measurements show already at room temperature that the anisotropy field of substituted compounds is higher with respect to pure SrFe 12 O 19 ferrite: the results can be expressed by a linear increase of the anisotropy field H a (x)= H a (0)(1+0.88 x) up to x=0.3; it appears that for x = 0.4 the anisotropy field remain practically the same indicating a saturation-type effect. The obtained anisotropy fields turn out to be in agreement with previous measurements [1] down to 200 K. This anisotropy behavior has never been observed in other Co substituted M-type and related compounds. In most cases the presence of Co ions in M, W, X or Z type ferrites was known to be responsible of high order terms in the magnetocrystalline anisotropy, but always in favor of planar or conical easy directions.…”

Section: Introductionsupporting

confidence: 91%

“…Attempts have been made to increase the magnetization at room temperature and to decrease the temperature coefficient of magnetization by a variety of substitutions in the place of Fe 3+ ions but with little success. Only recently new special types of hexagonal ferrites have been prepared by substitutions of La and Co in iron-ions lattice sites [1]. These compounds display significant improvements in the magnetic properties with respect to both Sr and Ba M-type ferrites.…”

Section: Introductionmentioning

confidence: 99%

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Anisotropy effects of La‐Co substitutions in M‐type Sr hexaferrites

Asti

Bolzoni

Breton

et al. 2004

phys. stat. sol. (c)

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In the present work we report on the anisotropy properties of Sr 1-x La x Fe 12-x Co x O 19 up to x=0.4. The study has been carried out on oriented polycrystalline samples by means of the Singular Point Detection techniques, the initial susceptibility, the magnetization curves and the differential susceptibility in the temperature range from 4.2 up to 300 K. The analysis of the results takes advantage of computer simulations based on an extended Stoner-Wohlfarth model and leads to the accurate determination of anisotropy constants K 1 , K 2 , K 3 and coefficients χ 2,0 , χ 4,0 , χ 6,0 , as functions of x and temperature. The results emphasise the strong effect of Co-ions on the high order anisotropy terms and are discussed in terms of the Slonczewski one-ion model.

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Section: Introductionsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Anisotropy effects of La‐Co substitutions in M‐type Sr hexaferrites

Asti

Bolzoni

Breton

et al. 2004

phys. stat. sol. (c)

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“…NdFeB magnet, the Fe 2 O 3 accounts for up to 90 wt% of Sr-ferrite. Sr-ferrite has the advantages of low cost raw material, so far is still the largest usage amount of permanent product [4][5][6] . The improvement of Sr-ferrite materials with respect to specific material properties or application fields is still a vital field of research.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Influence of Raw Material Fe2O3 on the Magnetic Properties of Sr-ferrite Magnets

Huang¹,

Hung²,

Kuo³

2016

J. Jpn. Soc. Powder Powder Metallurgy

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The influence of specific surface area (SSA) of Fe 2 O 3 was investigated while evaluating the raw material of Sr ferrite preparation. For hard ferrite magnet, SSA of Fe 2 O 3 was found markedly affects the grain growth and the magnetic properties. Increasing of SSA of Fe 2 O 3 resulted in the increase of remanence (B R ) and (BH) max , but also causes a decline in intrinsic coercive force ( i H C ). The SSA of Fe 2 O 3 is most important factor in determining the reactivity of the ferrite specimens during calcinations and sintering processes. A larger SSA promotes reactivity, which results in larger grain size of either calcined or sintered powder, consequently larger B R and smaller i H C were achieved, whereas, the opposite trend was observed for small SSA of Fe 2 O 3 . Results are also confirmed that, when less impurity in Fe 2 O 3 , the microstructure and magnetic properties of Sr-ferrite have smaller sensitivity to the SSA of Fe 2 O 3 . As found in this study, well control of raw material Fe 2 O 3 is shown to be very critical in tailoring suitable B R and i H C for customized Sr-ferrite manufacturing process.

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“…In order to decrease the weights of motors used in automobiles and to improve the efficiencies of motors used in electric appliances, many efforts have been made to improve the magnetic properties of ferrite magnets in recent years. [2][3][4][5] In order to further improve the magnetic properties of ferrite magnets, such as coercivity, remanent flux density, and maximum energy product, it is essential to understand the magnetization process. Previously, we successfully employed electron holography to statically observe the changes in the magnetic domain structures in Ba ferrite magnets by using a specially designed electromagnet capable of applying external magnetic fields.…”

Section: Introductionmentioning

confidence: 99%

In Situ Lorentz Microscopy and Electron Holography of Magnetization Process in Ferrite Magnets

Aiso

Shindo

Sato³

2007

Mater. Trans.

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The magnetic domain structures and magnetization processes of anisotropic Ba and Sr ferrite magnets are investigated by Lorentz microscopy and electron holography. By utilizing a sharp magnetic needle made of a sintered Nd-Fe-B magnet in a transmission electron microscope, the magnetization process in ferrite magnets is visualized for the first time by in situ Lorentz microscopy. In the anisotropic Ba ferrite specimen, magnetization reversal occurs suddenly along the grain boundaries over a large volume, which includes the volumes of some grains located around the specimen edges. On the other hand, in the anisotropic Sr ferrite specimen, magnetization reversal is not observed due to the large coercivity of the specimen. During the magnetization process from the demagnetized state in the Sr ferrite specimen, the domain wall inside a grain moves gradually along the grain boundary and then stops at the grain boundary.

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LaCo-substituted ferrite magnets, a new class of high-grade ceramic magnets; intrinsic and microstructural aspects

Cited by 192 publications

References 6 publications

Anisotropy effects of La‐Co substitutions in M‐type Sr hexaferrites

Anisotropy effects of La‐Co substitutions in M‐type Sr hexaferrites

Investigation of the Influence of Raw Material Fe<sub>2</sub>O<sub>3</sub> on the Magnetic Properties of Sr-ferrite Magnets

<I>In Situ</I> Lorentz Microscopy and Electron Holography of Magnetization Process in Ferrite Magnets

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