Studies of new rare-earth permanent magnets

Morrish, A. H.; Li, Z W; Zhou, X. Z.; Dai, Shouyu

doi:10.1088/0022-3727/29/9/010

Cited by 13 publications

(6 citation statements)

References 45 publications

(55 reference statements)

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“…The basic properties of R-Fe-B and R-Fe-C systems in various stages of researches were reviewed by Buschow ( , 1991b, Sagawa et al (1987a), Burzo and Kirchmayr (1989), Herbst (1991a), Burzo and Kirchmayr (1992), Wijn (1992) and Morrish et al (1996).…”

Section: Introductionmentioning

confidence: 99%

Permanent magnets based on R-Fe-B and R-Fe-C alloys

Burzo

1998

Rep. Prog. Phys.

210

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A review is given on the basic properties of 2:14:1 hard magnetic phases as well as technological procedures used for manufacturing R-Fe-B and R-Fe-C permanent magnets. First, we analyse the phase diagrams, crystal structure of hard magnetic phases and composition ranges in which these phases form solid solutions, as a result of various types of substitution. Then, the magnetic properties of R 2 Fe 14 B-, R 2 Fe 14 C-and R 2 Co 14 Bbased compounds are described. The routes used for manufacturing R-Fe-B and R-Fe-C permanent magnets are detailed. The magnets' microstructure as well as their coercivities are described in correlation with composition and manufacturing routes. The properties of nanostructure magnets are then presented. Finally, the stability of Nd-Fe-B and Nd-Fe-C magnets in various working conditions is analysed.

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Section: Introductionmentioning

confidence: 99%

Permanent magnets based on R-Fe-B and R-Fe-C alloys

Burzo

1998

Rep. Prog. Phys.

210

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“…As a conclusion of the M (T ) dependence obtained in our simulations let us emphasize that, in spherical particles, there is a surface layer with much higher degree of magnetic disorder than the core, which is the Ising version of the random canting of surface spins occurring in several fine particles with spinel structure [17,52,18,113,114]. However, our model does not evidence the freezing of this disordered layer in a spin-glass-like state below any temperature and size, in contrast with the suggestions given by some authors [21,24] and some experimental findings [21,23,53], for instance, the observation of shifted loops after an FC process (see Fig.…”

Section: Equilibrium Properties: Surface and Core Magnetisationssupporting

confidence: 59%

From Finite Size and Surface Effects to Glassy Behaviour in Ferrimagnetic Nanoparticles

Labarta

Batlle

Iglesias

Surface Effects in Magnetic Nanoparticles

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This chapter is aimed at studying the anomalous magnetic properties (glassy behaviour) observed at low temperatures in nanoparticles of ferrimagnetic oxides. This topic is discussed both from numerical results and experimental data. Ferrimagnetic fine particles show most of the features of glassy systems due to the random distribution of anisotropy axis, interparticle interactions and surface effects. Experiments have shown that the hysteresis loops display high closure fields with high values of the differential susceptibility. Low magnetisation as compared to bulk, shifted loops after field-cooling, highfield irreversibilities between zero-field and field cooling processes and ageing phenomena in the time-dependence of the magnetisation, are also observed. This phenomenology indicates the existence of some kind of freezing phenomenon arising from a complex hierarchy of the energy levels, whose origin is currently under discussion. Two models have been proposed to account for it: i) the existence of a spin-glass state at the surface of the particle which is coupled to the particle core through an exchange field; and ii) the collective behaviour induced by interparticle interactions. In real systems, both contributions simultaneously occur, being difficult to distinguish their effects. In contrast, numerical simulations allow us to build a model just containing the essential ingredients to study solely one of two phenomena. Glassy behaviour in ferrimagnetic nanoparticlesThe assemblies of fine magnetic particles with large packing fractions and/or nanometric sizes show most of the features which are characteristic of glassy systems (for a recent review see Ref. [12]). This glassy behaviour results from a complex interplay between surface and finite-size effects, interparticle interactions and the random distribution of anisotropy axis throughout the system. In many cases, these contributions are mixed and in competition, Sample characterisationThe phenomenology of the glassy state in strong interacting fine particles is illustrated through the study of the magnetic properties of nanocrystalline BaFe 10.4 Co 0.8 Ti 0.8 O 19 [11]. M -type barium ferrites have been studied for a long time because of their technological applications [33,34,35,36], such as microwave devices, permanent magnets, and high-density magnetic and magneto-optic recording media, as well as their large pure research interest [37,38]. The compounds obtained by cationic substitution of the pure BaFe 12 O 19 ferrite display a large variety of magnetic properties and structures, which go from collinear ferrimagnetism to spin-glass-like behaviour [37,39,38], depending on the degree of frustration introduced by cationic substitution. In particular, the BaFe 10.4 Co 0.8 Ti 0.8 O 19 compound seems to be ideal for perpendicular magnetic recording [40], since the Co 2+ -Ti 4+ doping scheme reduces sharply the high values of the coercive field of the pure compound, which precludes their technological applications. For this composition the magnetic structur...

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“…135 The resultant increase in this ratio is due to the volume expansion and opposing electron transfer from iron to nitrogen or carbon. Qi et al 136 139 it was found that in these compounds, cell volume increases by at least 4-6% over the Si range from 1 to 3. Addition of Si decreases the cell volume as well as the lattice parameters, and the result can be attributed to the increase in Curie temperature.…”

Section: Rare Earth Materialsmentioning

confidence: 98%

Study of materials using Mössbauer spectroscopy

Bandyopadhyay¹

2006

International Materials Reviews

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A comprehensive review is presented of the recent contributions Mo ¨ssbauer spectroscopy has made in materials science and engineering. After a brief introduction to the basic methodology, examples of the application of 57 Fe and 119 Sn Mo ¨ssbauer spectroscopy in both transmission and back-scattering mode are presented and discussed. Recent technological and software developments of this technique are also included. Coverage is further extended to recent, pertinent developments in space research and also in biological science and technology where Mo ¨ssbauer techniques are very widely used. Efforts have also been made to cover applications to archaeological samples where Mo ¨ssbauer spectroscopy is an important analytical tool.

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Studies of new rare-earth permanent magnets

Cited by 13 publications

References 45 publications

Permanent magnets based on R-Fe-B and R-Fe-C alloys

Permanent magnets based on R-Fe-B and R-Fe-C alloys

From Finite Size and Surface Effects to Glassy Behaviour in Ferrimagnetic Nanoparticles

Study of materials using Mössbauer spectroscopy

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