Analysis of the dependence of spin-spin correlations on the thermal treatment of nanocrystalline materials

Hernando, A.; Vázquez, M.; Kulik, T.; Prados, C.

doi:10.1103/physrevb.51.3581

Cited by 238 publications

(149 citation statements)

References 10 publications

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“…This alloy, of composition Fe 44 Co 44 Zr 7 B 4 Cu 1 , 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 nanocrystalline alloys are lost [3].…”

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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Section: Introductionmentioning

confidence: 99%

“…The ferromagnetic character of this matrix enables the exchange coupling between nanocrystals, which yield a severe reduction of the average magnetocrystalline anisotropy [2,3].…”

Section: Introductionmentioning

confidence: 99%

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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“…Nanocrystalline Fe-M-B type alloys, so called Nanoperm where M is an early transition metal, have been attractive for their excellent soft magnetic properties and are used as ultrasoft magnets in several commercial applications [1,2]. These good soft magnetic properties depend on the microstructure of the material [3,4].…”

Section: Introductionmentioning

confidence: 99%

Relationship between mechanical amorphization and boron integration during processing of FeNbB alloys

et al. 2014

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Fe75Nb10B15 alloys were prepared by mechanical alloying using different boron powders (crystalline B, commercial amorphous B, optimized amorphous B and intermetallic FeB) in the initial mixture, in order to study the boron incorporation into the Fe matrix and its influence on the amorphization of the alloys. Another composition with the same Fe/Nb ratio but whithout boron was prepared in order to differentiate between the influence of B and Nb in the evolution of microstucture and magnetic properties. Amorphization of samples was followed by X-ray diffraction and Mössbauer spectroscopy, concluding that only B-containing alloys develop an amorphous phase, while for the B-free alloy a supersaturated solid solution was observed as the final microstructure. Nb is rapidly incorporated into the matrix whereas remaining B inclusions are found at the end of the explored milling range for all B-containing samples. The amount of dissolved boron into the amorphous matrix was estimated from magnetic measurements, being the alloy prepared using FeB powder the one that most effectively dissolves this element.

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“…Soft magnetic nanocrystalline alloys, in which crystallites of about 10 nm are embedded in a residual amorphous matrix, have been developed as excellent candidates for soft magnetic applications [1]. This microstructure, which yields an averaging out of the magnetocrystalline anisotropy [2], is responsible for the outstanding magnetic properties observed. At the end of the last decade, new compositions FeCoMBCu, the so-called HITPERM alloys [3], extended the applicability of nanocrystalline alloys up to higher temperatures, due to the increase of the Curie temperature of the residual amorphous phase.…”

Section: Introductionmentioning

confidence: 99%

“…This microstructure, which yields an averaging out of the magnetocrystalline anisotropy [2], is responsible for the outstanding magnetic properties observed. At the end of the last decade, new compositions FeCoMBCu, the so-called HITPERM alloys [3], extended the applicability of nanocrystalline alloys up to higher temperatures, due to the increase of the Curie temperature of the residual amorphous phase.…”

mentioning

confidence: 99%

Effects of high temperature treatments in air and argon on the magnetic properties of HITPERM alloys

Blázquez¹,

Conde²,

Conde³

et al. 2006

Journal of Magnetism and Magnetic Materials

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The oxidation behavior of the HITPERM alloy series Fe 60 Co 18 Nb 6-x Zr x B 16-z Cu z (x = 0, 3, 6; z = 0, 1) was studied. After heating up to 1073 K, an oxide layer ~1 m thick with a two-layer structure (the outer enriched in Fe) can be identified previous to a sharp interface between the oxide layer and the alloy matrix, where no oxygen is detected. The alloys with Zr oxidize faster than the alloys without Zr. Magnetic properties of nanocrystalline samples annealed 20 h at 673 K in air and argon show no change. However, after 50 h at 773 K, the coercivity of the samples increases, the effect being more significant for the alloys without Zr than for those with Zr, independently of the gas environment during the annealing. No change was observed in the microstructure after annealing and, therefore, the magnetic hardening must be due to some changes in the residual amorphous matrix. Soft magnetic nanocrystalline alloys, in which crystallites of about 10 nm are embedded in a residual amorphous matrix, have been developed as excellent candidates for soft magnetic applications [1]. This microstructure, which yields an averaging out of the magnetocrystalline anisotropy [2], is responsible for the outstanding magnetic properties observed. At the end of the last decade, new compositions FeCoMBCu, the so-called HITPERM alloys [3], extended the applicability of nanocrystalline alloys up to higher temperatures, due to the increase of the Curie temperature of the residual amorphous phase. Although Cu addition is known to reduce the grain size in FINEMET and NANOPERM alloys through Cuclustering [1], Cu clusters do not form in Zr-containing HITPERM alloys [4]. However, Cu-clustering occurs and refines the microstructure of Nb-containing HITPERM alloys [5]. To check the real possibilities for high temperature technological applications of these materials the study of the compositional effects on the nanostructure stability [6] and the oxidation behavior of HITPERM-type alloys are key questions.In this work, the oxidation behavior in air and the effect of high temperature treatments in air and argon atmospheres on the microstructure stability of nanocrystalline Fe 60 Co 18 Nb 6-x Zr x B 16-z Cu z (x = 0, 3, 6; z = 0, 1) melt-spun ribbons (~ 5 mm wide and ~ 15-40 m thick) were studied. In the following the compositions will be denoted as Nb0 (x=0, z=0), Nb1 (x=0, z=1), NbZr1 (x=3, z=1) and Zr1 (x=6, z=1). The oxidation process was studied using a thermobalance (TG) Perkin-Elmer TGA7, in order to obtain the in-situ mass gain of the samples during the heat treatments. Scanning electron microscopy (SEM)

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Analysis of the dependence of spin-spin correlations on the thermal treatment of nanocrystalline materials

Cited by 238 publications

References 10 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

Relationship between mechanical amorphization and boron integration during processing of FeNbB alloys

Effects of high temperature treatments in air and argon on the magnetic properties of HITPERM alloys

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