Effect of Nb addition on the structure and soft magnetic properties of melt-spun Co69Fe7Si14B10 alloy

Melt-spun ribbons of Co₆₉Fe₇Si_14−xNb_xB₁₀ alloys with x=0, 2 and 4 have been prepared and characterized for structure and soft magnetic properties. Ribbons with x=0 and x=2 are found to be completely amorphous whereas the ribbon with x=4 contains irregular shaped faulted Co₂Si orthorhombic phase with grain size of about 100 nm. Nb addition is found to decrease the degree of amorphicity and induce perpendicular anisotropy, deteriorating the soft magnetic and magnetoimpedance properties.     

Effect of compositional variation on the soft magnetic properties of Fe(87−x−y)CoxTi7 Zr6By amorphous ribbons

The effect of the replacement of Fe by Co or B on the thermal stability and soft magnetic properties of the Fe-based amorphous metallic ribbons with Fe_(87−x−y)Co_xTi₇Zr₆B_y (x = 10, 20% and y = 8, 10, 12%) produced by melt-spinning technique was investigated. For the melt-spun amorphous ribbons, the values of saturation magnetization and coercivity were observed to range from 107.00 to 152.38 emu/g and from 0.012 to 0.446 Oe, respectively. The thermal properties such as T_g, T_x, and ΔT_x were in the range of 796.7–809.6 K, 840.2–853.5 K, and 35.8–54.5 K, respectively. In the Fe–Co–Ti–Zr–B alloys, the Co substitution for Fe improved the soft magnetic properties but decreased the thermal stability. For magnetic properties, the coercivity (H_c) decreased and saturation magnetization (M_s) increased by the addition of Co. However, the supercooled liquid region (ΔT_x) decreased by the addition of Co. Meanwhile, the B substitution for Fe had no meaningful change on the thermal stability and soft magnetic properties. The amorphous ribbon of Fe₅₉Co₂₀Ti₇Zr₆B₈ exhibited the best soft magnetic properties such as the low coercivity of 0.025 Oe and the high saturation magnetization of 152.38 emu/g.     

Effect of Cu additions on the magnetic properties and microstructure of FeCoNbB nanocrystalline alloy

The influence of Cu content and the annealing conditions in the (Fe_0.5Co_0.5)_85?x Nb₇B₈Cu _x (x=0.5, 1.0, 1.5) soft magnetic alloys on the magnetic properties and microstructure were investigated. The additions of Cu lower the primary and secondary crystallization temperatures and the α→γ phase transformation temperature of the FeCoNbB alloys. The (Fe_0.5Co_0.5)₈₄Nb₇B₈Cu₁ alloy annealed at 873 K for 3.6 ks, in which α-(Fe, Co) nanocrystalline phase with diameter of 5 nm precipitated from the amorphous matrix, shows the best soft magnetic properties. The resulting (Fe_0.5Co_0.5)₈₄Nb₇B₈Cu₁ nanocrystalline alloy exhibits a high saturation flux density of 1.88 T, low coercivity of 42 A/m, very high Curie temperature of 1240 K, as well as low core loss of 770 W/kg at 10 kHz under maximum magnetization of 1 T.     

Induced magnetic anisotropy in Co-doped Finemet-type nanocrystalline materials

Transverse magnetic anisotropy has been induced in the Fe_14.7Co_58.8Cu₁Nb₃Si_13.5B₉ and Fe_13.8Co₆₅Cu_0.6Nb_2.6Si₉B₉ amorphous ribbons by annealing under an external magnetic field. This anisotropy plays a predominant role, compared to magneto-crystalline and magneto-elastic anisotropies, in forming the magnetic properties and shaping the hysteresis loop. The effect of temperature and time of annealing on the induced magnetic anisotropy and magnetic properties (magnetic permeability, coercivity and power losses) in both alloys was investigated. Under this work, measurements of frequency dependence of the real and imaginary parts of magnetic permeability were made within a frequency range up to 110 MHz. It was found that as a result of magnetic field annealing the Snoek limit increases in both alloys compared to the Co-free Finemet.     

A metastable hard magnetic phase in the crystallization process of the Fe75Si11B10Nb3Sn1 alloy

A very interesting characteristic of FeSiB based amorphous alloys is its soft magnetic behavior. Most of these alloys remains soft along the crystallization process up to the nucleation of the iron borides. Examples of this are the widely studied Finemet and the FeSiBSn. In this work the crystallization of Fe₇₆Si₁₁B₁₀Nb₃ and Fe₇₅Si₁₁B₁₀Nb₃Sn₁ is studied by means of X-ray diffraction, Mössbauer spectroscopy and coercive magnetic field measurements after one hour isothermal annealing at different temperatures. In the crystallization process of the latter alloy a hard magnetic phase appeared when the samples were annealed above 773 K. The soft magnetic behavior was recovered after annealing at 873 K. The hyperfine parameters as well as the X-ray diffraction patterns are reported.     

Structural and magnetic study of bulk glassy Fe72 − x Co x B20Si4Nb4 alloys

The influence of the partial replacement of Fe by Co on the structural and magnetic properties of bulk-type glassy Fe_72???x Co _x B₂₀Si₄Nb₄ (x = 0, 5, 10, 15, 20, 25, 30, 35) alloys has been studied using differential scanning calorimetry (DSC), X-ray diffraction (XRD) magnetic measurements and Mössbauer spectroscopy. Results show that the successive Co addition: (1) does not affect the mass density of the studied alloys, (2) affects appreciably the super cooled region, (3) modifies the magnetic properties, exhibiting soft magnetic behavior, (4) modifies the spin texture and disorder within the studied specimens.     

具有宽过冷液相区的Fe62Co8-x(Cr,Mo)xNb4Zr6B20非晶态合金的热稳定性与磁性

根据制备块状非晶态合金的三条经验准则,选择了成分为Fe₆₂Co_8-xCr_xNb₄Zr₆B₂₀和Fe₆₂Co_8-xMo_xNb₄Zr₆B₂₀(x=0,2,4)的合金系.利用单辊急冷法制备出厚为30μm宽为5mm左右的条带,并用差热分析、X射线衍射以及 关键词： 过冷液相区 铁磁性 非晶态合金     

Nanocrystals magnetic contribution to FINEMET-type soft magnetic materials with Ge addition

Over the last years several works have been published in which magnetic and structural properties of soft magnetic nanocrystalline alloys were reported. Among these, there are a series of articles where the nanocrystals composition of FINEMET-type alloys with Ge addition was obtained by Mössbauer spectroscopy (MS) and X-ray diffraction (XRD). By considering a linear relationship between the magnetic moments of the nanocrystals and the composition of various elements in these crystallites, the magnetic moment of the nanocrystals was calculated. This paper reviews results obtained by different authors since 1980 and they are compared with ours. In turn, we revised some elements not previously considered for the calculus of the nanocrystals composition that allowed us to obtain the magnetic moment of the crystallites in the alloy. In particular, we analyzed FINEMET-type alloys with replacement of B for Ge: Fe_73.5Si_13.5Ge₂B₇Nb₃Cu₁ and Fe_73.5Si_13.5Ge₄B₅Nb₃Cu₁. The nanocrystalline structure was obtained by isothermal annealing of melt-spun ribbons at 823 K for 1 h. From MS and XRD we obtained the atomic composition of the nanocrystals in the magnetic material. The magnetic contribution of the nanocrystals to the alloy was calculated using a linear model and the results were compared with experimental measurements of the samples.     

Effect of the addition of Ge to the FINEMET alloy

The results obtained by partially substituting Ge for B and Si in the FINEMET alloy for the purpose of improving its magnetic properties at high temperatures are presented in this work. Nanocrystalline ribbons were obtained from controlled crystallization of amorphous material made employing the melt spinning technique. The studied compositions were: Fe_73.5Si_13.5Ge₂Nb₃B₇Cu₁ and Fe_73.5Si_13.5Ge₄Nb₃B₅Cu₁. The structural evolution of these alloys was studied using X-ray diffraction (XRD) and differential scanning calorimetry (DSC) and these results were correlated with their magnetic properties at different annealing temperatures. The coercivity obtained for both alloys was below 1 A/m at anneling temperatures between 773 and 823 K. The amorphous saturation magnetization was satisfactory, almost 137 emu/g, comparable with that obtained for FINEMET alloys. The nanocrystallization and the Curie temperatures are dependent on Ge concentration.     

Magnetocaloric and magnetoresistance properties in Co-based (Co0.402Fe0.201Ni0.067B0.227Si0.053Nb0.05)100−xCux (x=0–1) glassy alloys

The magnetocaloric and magnetoresistance properties of amorphous Co-based (Co_0.402Fe_0.201Ni_0.067B_0.227Si_0.053Nb_0.05)_100?xCu_x (x = 0, 0.5, 0.75 and 1) ribbons were investigated. Cu additions changed the crystallisation temperature (T_x) and the Curie temperature (T_C). The saturation magnetisation (M_s) and coercivity (H_c) for alloys were in the range of 65.51–38.49 emu/g and 1.99–6.84 A/m, respectively. Under an applied magnetic field change of 2.2 T, the (?ΔS_M)^max for (Co_0.402Fe_0.201Ni_0.067B_0.227Si_0.053Nb_0.05)_100?xCu_x with x = 0, 0.5, 0.75 and 1 are 0.77, 0.71, 0.89 and 0.67 Jkg^?1 K^?1, respectively. The values of refrigeration capacity (RC) for the as-spun glassy alloys are comparable with those of previously studied Fe-based metallic glasses such as Fe₈₀B₁₀Zr₉Cu₁, (Fe_0.76B_0.24)₉₆Nb₄ and Fe₈₂Ni₂Zr₆B₁₀. In addition, the maximum magnetoresistance (MR) values for (Co_0.402Fe_0.201Ni_0.067B_0.227Si_0.053Nb_0.05)_100?xCu_x with x = 0, 0.5, 0.75 and 1 are found to be 110, 38, 23 and 1% around the Curie temperatures under an applied magnetic field change of 1 T, respectively. With good RC, negligible hysteresis due to very low coercivity values and large magnetoresistance, these Co-based amorphous alloys can be used as the high temperature magnetic refrigerants and multifunctional applications working in the temperature range of 450–600 K.     

Coercivity and induced magnetic anisotropy by stress and/or field annealing in Fe- and Co- based (Finemet-type) amorphous alloys

Uniaxial magnetic anisotropy has been induced in amorphous Fe_73.5Cu₁Nb₃Si_15.5B₇ (Fe-rich) and (Co₇₇Si_13.5B_9.5)₉₀Fe₇Nb₃ (Co-rich) ferromagnetic alloys by annealing under stress and/or magnetic field. Such anisotropy plays a crucial role on the magnetization process and, consequently, determine the future applications of these materials. The mechanisms involved on the origin of such induced magnetic anisotropy showed significant differences between Fe-rich and Co-rich amorphous alloys. This work provides a comparative study of the coercive field and induced magnetic anisotropy in Fe-rich and Co-rich (Finemet) amorphous alloys treated by stress and/or field.     

Soft magnetic properties and giant magneto-impedance effect of Fe73.5−xCrxSi13.5B9Nb3Au1 (x=1–5) alloys

In this paper, the effect of microstructural and surface morphological developments on the soft magnetic properties and giant magneto-impedance (GMI) effect of Fe_73.5−xCr_xSi_13.5B₉Nb₃Au₁ (x=1, 2, 3, 4, 5) alloys was investigated. It was found that the Cr addition causes slight decrease in the mean grain size of α-Fe(Si) grains. AFM results indicated a large variation of surface morphology of density and size of protrusions along the ribbon plane due to structural changes caused by thermal treatments with increasing Cr content. Ultrasoft magnetic properties such as the increase of magnetic permeability and the decrease of coercivity were observed in the samples annealed at 540 °C for 30 min. Accordingly, the GMI effect was also observed in the annealed samples.     

Rapid stress annealing dependence of structural and magnetic properties of Fe75 − x Co x Cu1Nb3Si15B6 alloys

Structural and magnetic properties of nanocrystalline Fe_75???x Co _x Cu₁ Nb₃Si₁₅B₆ (x?=?0, 2, 5) alloys are reported using magnetic measurements X-ray diffraction, Mössbauer spectroscopy. Results show that: (1) for the specimens with x?=?0 reveal that the volume fraction of the nanograins and their grain diameter ranges between 56% and 80% and 10 and 18 nm, (2) annealing above 700°C apart from Fe₃Si type nanocrystals, magnetically hard Fe₃B, Fe₂₃B phases also appear, leading to a sharp increase of the coercive field, (3) Co content and applied stress during annealing has considerable effect on relative permeability and stress induced anisotropy, which is perpendicular to the ribbon axis, Mössbauer spectroscopy also suggests changes in spin texture.     

Severe plastic deformation of amorphous alloys: II. Magnetic properties

The influence of severe plastic deformation in a Bridgman cell on the magnetic properties of amorphous alloys of metal-metalloid type, Ni₄₄Fe₂₉Co₁₅Si₂B₁₀, Fe₇₄Si₁₃B₉Nb₃Cu₁, Fe_57.5Ni₂₅B_17.5, Fe_49.5Ni₃₃B_17.5, and Fe₇₀Cr₁₅B₁₅, obtained by melt spinning, has been investigated. It is found that the saturation magnetization significantly changes (increases or decreases), depending on the number of ferromagnetic and antiferromagnetic components in the alloy. It is suggested that very high shear stress causes internal phase decomposition in the amorphous matrix into nanoscale regions, enriched or depleted with ferromagnetic components.     

Structure and magnetic properties of hot pressed Co-based powder

Coarse-grained powders, prepared by short-time milling of Co_70.3Fe_4.7Si₁₀B₁₅ amorphous ribbons, were consolidated by hot pressing into disc-shaped specimens. The influence of the consolidation temperature on the structure and the magnetic properties of the bulk specimens was investigated. The lowest value of coercivity of 23 A/m was achieved for samples prepared by consolidation of the powder in the supercooled liquid region at a temperature of 813 K. In order to increase the saturation magnetic polarization crystalline iron powder was added to the amorphous Co_70.3Fe_4.7Si₁₀B₁₅ powder.     

Annealing effect on soft magnetic properties and magnetoimpedance of Finemet Fe73.5Si13.5B9Nb3Au1 alloy

Effect of annealing on the soft magnetic properties of Fe_73.5Si_13.5B₉Nb₃Au₁ amorphous ribbon has been investigated by means of structure examination, magnetoimpedance ratio (MIR) and incremental permeability ratio (PR) spectra measured in the frequency range of 1–10 MHz at a fixed current of 10 mA X-ray diffraction analysis showed that the as-cast sample was amorphous and it became nanocrystalline under a proper heat treatment. When annealing amorphous alloy at 530 °C for 30, 60, 90 min, soft magnetic properties have been improved drastically. Among the samples investigated, the sample annealed at 530 °C for 90 min showed the softest magnetic behavior. The MIR and PR curves revealed the desirable changes in anisotropy field depending upon annealing.     

Magnetic domain structure in Fe78.8−xCoxCu0.6Nb2.6Si9B9 nanocrystalline alloys studied by Lorentz microscopy

The magnetic domain structures of Fe_78.8−xCo_xCu_0.6Nb_2.6Si₉B₉ (x=0, 20, 40, 60) alloys are investigated by Lorentz microscopy coupled with the focused ion beam method. The specimen prepared using the FIB method is found to have a considerably more uniform thickness compared to that prepared using the ion-milling method. In Fe_38.8Co₄₀Cu_0.6Nb_2.6Si₉B₉ and Fe_18.8Co₆₀Cu_0.6Nb_2.6Si₉B₉ alloys, 180° domain walls extending in the direction of the induced magnetic anisotropy are observed. Analysis with Lorentz microscopy reveals that the width of the magnetic domains decreases with an increase in the cobalt content or the induced magnetic anisotropy K_u, that is, the domain width d is proportional to the induced magnetic anisotropy (K_u)^−1/4. On the other hand, in the in situ Lorentz microscopy observation as a function of temperature, magnetic ripple structures are found to appear in a localized area due to the fluctuation of magnetization vectors from 423 K. It is observed that the induced magnetic anisotropy caused by the applied magnetic field at 803 K is not suppressed by the magnetic ripple structures observed at 423–443 K.     

Magnetic properties and temperature stability of a molybdenum-doped finemet-type alloy

The influence of nanocrystallization conditions on the structure, magnetic properties, and temperature stability of nanocrystalline magnetically soft Fe_73.5Cu₁Nb_1.5Mo_1.5Si_13.5B₉ alloy is studied. It is found that preliminary low-temperature annealing exerts an influence on subsequent nanocrystallization of the alloy. In addition, preannealing followed by nanocrystallization considerably improves the magnetic properties of the alloy. It is shown that the magnetic properties of the material can be controlled by varying the frequency of a magnetic field used for thermal treatment causing nanocrystallization. It is established that the magnetic properties of nanocrystalline Fe_73.5Cu₁Nb_1.5Mo_1.5Si_13.5B₉ alloy offer a high temperature stability.     

Structure and magnetic properties of iron-and cobalt-based amorphous alloys versus nanocrystallization conditions

The effect of the structural state of Fe₅Co₇₀Si₁₅B₁₀, Fe₆₀Co₂₀Si₅B₁₅, and Co_81.5Mo_9.5Zr₉ amorphous alloys on their magnetic properties is studied under different nanocrystallization conditions. A permanent magnetic field applied during thermomagnetic treatment is found to affect structuring in the amorphous alloys at the initial stage of devitrification. The fine structure of the devitrified amorphous alloys is shown to correlate with the field shifting the hysteresis loop. A mechanism accounting for a hysteresis loop shift in amorphous alloys is discussed.     

Fe-Cu-Nb-Si-B纳米晶体软磁材料中有效磁各向异性的测定

研究了成分为Fe_73.5Cu₁Nb₃Si_13.5B₉的纳米晶体结构的软磁材料的磁各向异性。理论分析及测量结果说明,用趋近饱和的磁化过程可以测定出这种材料中的有效磁各向异性常数,它比晶粒中的磁晶各向异性常数K₁约小一个数量级。 关键词：