Amorphous and nanocrystalline materials for applications as soft magnets

McHenry, Michael E.; Willard, M. A.; Laughlin, David E.

doi:10.1016/s0079-6425(99)00002-x

Cited by 1,498 publications

(897 citation statements)

References 247 publications

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“…respectively. These values are similar to those found for NANOPERM and HITPERM alloys [1,[22][23][24]. The value of the Avrami exponent of the nanocrystallization process is close to 1 for all the studied alloys.…”

supporting

confidence: 87%

“…The value of the Avrami exponent of the nanocrystallization process is close to 1 for all the studied alloys. This value is characteristic for the kinetics of the nanocrystallization of metallic amorphous alloys [1,22,23].The shape of the peak of the second transformation stage is clearly asymmetric for the alloys with Ge (much clearer for the alloy with 20 at. % of Co), while it is sharp and symmetric for the alloys without Ge.…”

mentioning

confidence: 88%

“…Nanocrystalline Fe-based alloys exhibit outstanding soft magnetic properties characterized by a very low coercivity and a very high saturation magnetization [1]. These alloys have a microstructure in which nanocrystals of a ferromagnetic -Fe type phase (~10 nm in size) are embedded in a residual amorphous matrix, also ferromagnetic but with a lower…”

Section: Introductionmentioning

confidence: 99%

“…The original compositions have been slightly modified by the addition of other elements, in order to achieve specific characteristics for different applications [1]. In particular, since the production of HITPERM alloys by Willard et al in 1998 [6], the extension of the applicability of nanocrystalline alloys to higher temperatures is becoming an intensive area of research in the recent years.…”

Section: Introductionmentioning

confidence: 99%

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Partial substitution of Co and Ge for Fe and B in Fe–Zr–B–Cu alloys: microstructure and soft magnetic applicability at high temperature

et al. 2005

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The partial substitutions of Co for Fe and Ge for B are studied for a Fe 83-x Co x Zr 6 B 10-y Ge y Cu 1 alloy series (x = 0, 5 and 20; y = 0 and 5) as a possible way to enhance the high temperature applicability of NANOPERM alloys. The devitrification process, the nanocrystallization kinetics and the nanocrystalline microstructure are similar for all the studied alloys. Good soft magnetic properties are observed even at a high crystalline volume fraction of bcc -Fe nanocrystals, which are stable up to ~1000 K. The partial substitution of Co for Fe is very effective to increase the Curie temperature of the residual amorphous matrix (T C AM ). Although the substitution of Ge for B is ineffective to increase T C AM , a clear increase of the saturation magnetization with respect to the Ge-free alloy can be observed. These nanocrystalline compositions have a high concentration of Fe and a typical composition: Fe-M-ET-(Cu), where M is a metalloid and ET is an early transition metal. The addition of metalloids, such as B, P, Si, etc., is necessary to enable the production of a precursor amorphous alloy by rapid quenching techniques, from which the nanocrystalline microstructure is obtained after controlled crystallization. It is important to distinguish two different kinds of metalloids: those highly soluble in the -Fe phase (e.g. Si) and those whose solubility in this phase is very restricted (e.g. B). The former elements will be generally dissolved in the crystalline phase, increasing the crystalline volume fraction but deteriorating some magnetic properties like the saturation magnetization and the Curie temperature of the crystalline phase. The latter elements will remain in the amorphous matrix and will diminish the maximum volume fraction of nanocrystals, although preserving the purity of the -Fe phase.The early transition metals (Zr, Nb, Hf, etc.) have a very low solubility in the -Fe phase and, consequently, will remain in the amorphous matrix. However, due to the very slow diffusivity of these elements in the amorphous phase, they pile up at the crystal-matrix interface and constrain the growth of the crystalline phase to the nanocrystalline scale. was proposed mainly because of the strong increase of the Curie temperature of the residual amorphous phase (T C AM ) due to the partial substitution of Co for Fe with respect to the Cofree NANOPERM alloy [7]. In fact, the exchange coupling between nanocrystals is transmitted through the ferromagnetic residual amorphous matrix and thus, at temperatures above the Curie temperature of this residual amorphous matrix, the nanocrystals become exchange uncoupled and, consequently, the outstanding soft magnetic properties of these In this work, the combined effect of partial substitution of Co for Fe and Ge for B on the microstructure and the magnetic properties of nanocrystalline alloys is studied. The maximum Co concentration studied in the alloys is 20 at. %, in order to search for a new showed that this parameter is seriously deteriorated for higher Co con...

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supporting

confidence: 87%

mentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Partial substitution of Co and Ge for Fe and B in Fe–Zr–B–Cu alloys: microstructure and soft magnetic applicability at high temperature

et al. 2005

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“…FeCoB based amorphous alloys that demonstrate so called soft magnetic properties proved to be of special interest [11][12][13][14]. The amorphous tapes based on FeCoB experience significantly lower losses during magnetization reversal than FeSi transformer steels used in the electro technical industry [15]. In addition these materials demonstrate almost zero magnetostriction and, depending on the chemical composition, relatively high saturation magnetization.…”

Section: Introductionmentioning

confidence: 99%

Effect of structural relaxations within the amorphous structure on the magnetic properties of amorphous tapes from FeCoB family

Szota

2017

Archives of Metallurgy and Materials

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The paper presents the research results for the Fe 78 Co 2 Si 9 B 11 amorphous alloy, and after the process of annealing resulting only in the relaxation of the material. The structure relaxations occurring in the volume of test samples lead to the changes in their magnetic and mechanic properties. Therefore the studies on the effect of the structure defects on the properties of these type of materials are important. Understanding the processes occurring during the magnetizing of amorphous alloys can be helpful in the design of modern functional materials for special purposes. The main purpose of this elaboration was to determine the effect of the amorphous structure defects in the state after solidification and after heat treatment on the changes in the magnetizing process and in such parameters as the saturation magnetization and the coercivity field.

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Magnetic Decoupling in Nanocrystalline Systems

Vincze

Kemény

Kaptás

et al. 2002

phys. stat. sol. (a)

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Anomalous composition dependences of the Curie temperature of the residual amorphous phase in nanocrystalline Fe 92--x B x Zr 7 Cu 1 (2 x 23) alloys were studied by Mö ssbauer and magnetization measurements. The observed large (almost 300 K) increase with respect to that of the precursor amorphous phase at low B content is attributed to the volume effect. Mö ssbauer line broadening shows the presence of superparamagnetic relaxation of the bcc magnetization in nanocrystalline Fe 74 B 18 Zr 7 Cu 1 well below the Curie temperature of the residual amorphous phase suggesting that interphase exchange coupling is weaker than the dipolar magnetic fields.

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Amorphous and nanocrystalline materials for applications as soft magnets

Cited by 1,498 publications

References 247 publications

Partial substitution of Co and Ge for Fe and B in Fe–Zr–B–Cu alloys: microstructure and soft magnetic applicability at high temperature

Partial substitution of Co and Ge for Fe and B in Fe–Zr–B–Cu alloys: microstructure and soft magnetic applicability at high temperature

Effect of structural relaxations within the amorphous structure on the magnetic properties of amorphous tapes from FeCoB family

Magnetic Decoupling in Nanocrystalline Systems

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