Microstructures and soft magnetic properties of Fe80P20-xSix (x = 4.5–6.5) amorphous ribbons

Fe-based amorphous ribbons with excellent soft magnetic properties and mechanical properties were prepared in the Fe–Si–P ternary system. Enhanced soft magnetic properties could be achieved through annealing treatment of the ribbons for 1 h at 325 °C, which is far below the glass transition temperatures (462–474 °C). Icosahedral medium-range ordering with a size range of around 2 nm occurred throughout the amorphous matrix during the low-temperature annealing treatment. The annealed ribbons exhibited improved magnetic saturation of over 185 emu/g while maintaining good mechanical flexibility. During icosahedral ordering, the distance between the Fe atoms and the coordination number within the amorphous ribbon can be optimised for achieving high magnetic saturation. However, nanocrystallisation of the SiP and Fe₂P transition phases embedded within the amorphous matrix occurred after the annealing treatment for 1 h at 385 °C, which caused deterioration of the soft magnetic properties and mechanical flexibility of the ribbons. Therefore, the combination of high magnetic saturation and mechanical flexibility of the amorphous ribbons could be optimised through low-temperature annealing treatment without any nanocrystallisation.     

Mössbauer spectroscopical investigation of amorphous Fe–Y alloy ribbons prepared by melt spinning

Fe–Y amorphous alloy ribbons were prepared by the melt spinning method and characterized by X-ray diffraction, Mössbauer spectroscopy and inelastic neutron scattering. X-ray diffraction demonstrates that the Fe_0.7Y_0.3 ribbons are completely amorphous, whereas the Fe_0.3Y_0.7 ribbons contain a small fraction of crystalline Y precipitates in the amorphous Fe–Y matrix. Mössbauer spectroscopy between 4.2 to 300 K reveals the amorphous nature of the Fe–Y matrix and the Fe_0.7Y_0.3 ribbons. The preliminary neutron scattering results S(Q, ω) show excess low energy vibrational modes which gives rise to the so called “boson peak” in this amorphous material.     

应力退火Fe基纳米晶薄带横向磁各向异性的介观结构研究

用原子力显微镜(AFM)观测了不同张应力退火的Fe基纳米晶(Fe_73.5Cu₁Nb₃Si_13.5B₉)薄带横断面的形貌，并结合X射线衍射(XRD)图谱对不同张应力退火的Fe基纳米晶薄带的介观结构进行分析；测量了不同张应力退火Fe基纳米晶薄带的纵向驱动巨磁阻抗(LDGMI)曲线及横向磁各向异性场；认为张应力退火Fe基纳米晶薄带感生横向磁各向异性场的介观结构机理，是由于外加张应力退火产生由非晶相包裹着的α-Fe(Si)纳米晶粒(包裹晶粒)的横向优势团聚. 关键词： 应力退火 介观结构 AFM 团聚     

Superparamagnetic Relaxation in Nanocrystalline Fe80Zr7B12Cu1 Alloys

Nanocrystalline Fe₈₀Zr₇B₁₂Cu₁ alloys with different amounts and sizes of bcc precipitates were prepared by appropriate annealing of amorphous ribbons. The 6–10 nm ferromagnetic bcc granules are embedded in a residual amorphous tissue with a thickness at least 4 nm. Above room temperature superparamagnetic relaxation characteristic for small magnetic particles was observed with increasing temperature, as indicated by a significant increase in the width of the Mössbauer lines belonging to the bcc precipitates. It shows the absence of magnetic coupling which is stronger than the dipole-dipole interaction between the ferromagnetic nanoparticles.

     

Hyperfine field relaxations in the Fe−Co−B amorphous alloys

A systematic increase of the average hyperfine magnetic induction at⁵⁷Fe measured at room temperature during interrupted isothermal annealing was found to be inherent to the irreversible relaxation processes in the Fe−B based soft magnetic alloys at moderately elevated temperatures. Assuming superimposed asymptotic exponential field vs. time dependences. several processes can be distinguished, their relaxation times determined and from the Arrhenius-like log τ vs. 1/T plots average activation enthalpies estimated. Results on the Fe₇₀Co₁₀B₂₀ and Fe_85−x Co _x B₁₅ (x=17, 19 and 21 at. % Co) amorphous ribbons between 100 and 200°C are compared and discussed in terms of possible stress relief, free volume annihilation and short range ordering mechanisms.     

Mössbauer investigation of amorphous-to-crystalline transformation of Fe62Ni16B14Si8 by isothermal annealing

Room temperature transmission Mössbauer spectra of Fe₆₂Ni₁₆B₁₄Si₈ ribbons, annealed in vacuum for time periods ranging from 5 to 60 minutes at the crystallization temperatureT _x=720 K, have been used to investigate the crystallization mechanism by isothermal annealing. Reorientation of the magnetic anisotropy almost normal to the ribbon plane was observed and correlated to the annealing time dependence of the mean hyperfine field (HF) of the amorphous component. Crystallization started at the surface before the bulk and was found to occur in two steps: a metastable equilibrium of the amorphous phase with (FeNi), (FeNi)Si and t-(FeNi)₃B, followed by the decomposition of t-(FeNi)₃B into t-(FeNi)₂B and (FeNi). The increase of the mean magnetic moment at the Fe sites as compared to related iron-based alloys was attributed to compositional small Ni additions.     

Influence of Nb substitution for Fe on the magnetic and magneto-impedance properties of amorphous and annealed Fe76.5−xSi13.5B9Cu1Nbx (x=0–7) ribbons

We report a systematic study of the influence of Nb substitution for Fe on the magnetic properties and magneto-impedance (MI) effect in amorphous and annealed Fe_76.5−xSi_13.5B₉Cu₁Nb_x (x=0, 1, 2, 3, 4, 5, 6, and 7) ribbons. The amorphous ribbons were annealed at different temperatures ranging from 530 to 560 °C in vacuum for different annealing times between 5 and 20 min. We have found that for the as-quenched amorphous ribbons, the substitution of Nb for Fe first increases the saturation magnetization (M_s) and decreases the coercivity (H_c) until x=3, for which the largest M_s∼152 emu/g and the smallest H_c∼1.3 Oe are obtained, then an opposite trend is found for x>3. The largest MI ratio (ΔZ/Z∼38% at f=6 MHz) is achieved in the amorphous ribbon with x=3. A similar trend has been observed for the annealed ribbons. The most desirable magnetic properties (M_s∼156 emu/g and H_c∼1.8 Oe) and the largest MI ratio (ΔZ/Z∼221% at f=6 MHz) are achieved for the x=3 sample annealed at 540 °C for 15 min. A correlation between the microstructure, magnetic properties, and MI effect in the annealed ribbons has been established.     

Optical properties and the magnetoimpedance effect in amorphous Co-Ni-B metal alloys

A magnetoimpedance effect is observed in Co_80–xNi_xB20 (x = 4, 6, 8, 10, 12) amorphous metal alloy ribbons when an alternating current at frequencies ranging from 1–3000 kHz is passed through samples in an external magnetic field. Spectra of the permittivity and optical conductivity of the surface of ribbons of these alloys are obtained for incident photon energies of 1.0–5.0 eV. The relationships between the magnitude of the magnetoimpedance effect, and the magnetic properties, electronic structure parameters, and optical characteristics of the amorphous alloy samples are determined.     

Hyperfine interactions in nanocrystallized NANOPERM-type metallic glass containing Mo

NANOPERM-type alloy with chemical composition Fe₇₆Mo₈CuB₁₅ was studied by combination of ⁵⁷Fe Mössbauer spectroscopy and ⁵⁷Fe(¹⁰B, ¹¹B) nuclear magnetic resonance in order to determine distribution of hyperfine magnetic fields and evolution of relative concentration of Fe-containing crystalline phases within the surface layer and the volume of the nanocrystallized ribbons with annealing temperature. Differential scanning calorimetry revealed two crystallization stages at T_x1 ～ 510 ^°C and T_x2 ～ 640 ^°C, connected to precipitation of α-Fe and Fe(Mo,B) nanocrystals, respectively. The amorphous and partially crystalline state was obtained by annealing at several temperatures in the range 510-650 ^°C. The combination of conversion electron (CEMS) and transmission Mössbauer spectrometry (TMS) showed that annealing induces crystallization starting from both surfaces of the ribbons. For the as-quenched sample, scanning electron microscopy (SEM) and CEMS revealed significant differences in the “air” and “wheel” sides of the ribbons, crystallites were preferentially formed at the latter. While SEM micrographs of annealed samples showed various mean diameters of the crystals at opposite sides of the ribbons, the amounts of crystalline volume derived from the CEMS spectra approximately equaled. Mössbauer spectra of annealed samples contained narrow sextet ascribed to crystalline α-Fe phase, three sextets with distribution of hyperfine field assigned to the interface regions of the nanocrystals and the contribution of the amorphous phases. In-field TMS performed at 4.2 K with magnetic moments aligned by external magnetic field enabled to properly determine in particular the contribution of the amorphous phases in the samples. Resulting distributions of the hyperfine fields were compared with ⁵⁷Fe(¹⁰B, ¹¹B) nuclear magnetic resonance (NMR) spectra.     

Shear band formation and fracture behavior of nanocrystalline (Co,Fe)-based alloys

The crystal structure, crystallization, fracture behavior and mechanical properties of (Co_{1 ? x} Fe _x )₈₉Zr₇B₄ (x = 0–0.7) nanocrystalline ribbons were investigated. The crystallization peaks of the amorphous ribbons tend to shift to higher temperatures with increasing Fe content. After annealing at 475°C for 3600 s, the main crystallization product is hcp-(Co,Fe) for the Co-rich composition (x = 0), bcc-(Co,Fe) for high Fe contents (x ≥ 0.3) and a mix of bcc, and fcc for intermediate compositions (0.025 ≤ x ≤ 0.15). The relative strain at fracture decreases dramatically (ε_f < 0.01) for x ≥ 0.15, whereas for lower Fe content it has a maximum (ε_f > 0.037) at x = 0.025 and 0.050 resulting in excellent resistance against fracture. The brittle ribbons (x ≥ 0.15) showed smooth fracture surface with dimples less than 230 nm in diameter, small localized or absent shear bands and large Vickers hardness (>1200 kg mm^?2). On the other hand, the Co-rich ribbons with greater ductility (x = 0.025, 0.05) exhibit a vein pattern filled with voids (features ～2–11 µm), extensive shear banding and lower Vickers hardness (<1050 kg mm^?2).     

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.     

Pr2Fe14(C,B)/α-(Fe,Co)型纳米晶复合磁体的结构与磁性

研究了Pr_xFe_82-x-yTi_yCo₁₀B₄C₄ (x=9—10.5;y=0, 2)纳米晶薄带的结构与磁性. 结果表明,所有薄带皆主要由2∶14∶1, 2∶17和α-(Fe, Co)三相组成. 对于y=0的合金,其内禀矫顽力随Pr含量x的增加而增加,剩磁随Pr含量x的增加而减小. 以Ti置换部分Fe (y=2),合金的磁性能得到显著提高,表现为:添加Ti后,合金的剩磁B_r基本不降低,x=10.5时合金的B_r值甚至有较明显的提高;同时添加Ti后,合金的内禀矫顽力及退磁曲线的方形度都明显改善. 当x=10.5,y=2时,合金薄带的磁性能达到最佳值为: B_r=9.6 kGs(1 Gs=10^-4 T),_iH_c =10.2 kOe(1 Oe=79.5775 A/m)和(BH)_max＝17.4 MGOe. 随着Pr含量的提高,合金中的硬磁相2 ∶14 ∶1的含量相对增加,内禀矫顽力提高;而Ti置换Fe抑制了软磁相α-(Fe, Co)在快淬和热处理过程中的优先长大,使合金中软磁相和硬磁相的晶粒尺寸及比例趋向最佳组合,交换耦合作用明显增强. 关键词： 纳米晶永磁材料 2Fe₁₄(C')" href="#">Pr₂Fe₁₄(C B) Ti添加 交换耦合     

Influence of crystallization treatment on structure,magnetic properties and magnetocaloric effect of Gd71Ni29 melt-spun ribbons

The influence of crystallization treatment on the structure, magnetic properties and magnetocaloric effect of Gd₇₁Ni₂₉ melt-spun ribbons has been investigated in detail. Annealing of the melt-spun samples at 610 K for 30 min, a majority phase with a Fe₃C-type orthorhombic structure (space group, Pnma) and a minority phase with a CrB-type orthorhombic structure (space group, Cmcm) were obtained in the amorphous matrix. The amorphous melt-spun ribbons undergo a second-order ferromagnetic to paramagnetic phase transition at 122 K. For the annealed samples, two magnetic phase transitions caused by amorphous matrix and Gd₃Ni phases occur at 82 and 100 K, respectively. The maximum magnetic entropy change (–ΔS_M)^max is 9.0 J/(kgˑK) (5T) at 122 K for the melt-spun ribbons. The values of (–ΔS_M)^max in annealed ribbons are 1.0 and 5.7 J/(kgˑK), corresponding to the two adjacent magnetic transitions.     

FeSiBP bulk metallic glasses with high magnetization and excellent magnetic softness

Fe-based amorphous alloy ribbons are one of the major soft magnetic materials, because of their superior magnetic properties such as the relatively high saturation magnetization (J_s) of 1.5–1.6 T and good magnetic softness. However, the preparation of the ordinary amorphous magnetic alloys requires cooling rates higher than 10⁴ K/s due to the low glass-forming ability (GFA) and thus restricts the material outer shape. Recently, Fe-metalloid-based bulk metallic glasses (BMGs) containing glass-forming elements such as Al, Ga, Nb, Mo, Y and so forth have been developed. These alloys have high GFA, leading to the formation of BMG rod with diameters of mm-order. However, the glass-forming metal elements in BMGs result in a remarkable decrease in magnetization. Basically, J_s depends on Fe content; hence, high J_s requires high Fe content in the Fe-based amorphous alloys or BMGs. On the other hand, high GFA requires a large amount of glass-forming elements in the alloys, which results in lower Fe content. Therefore, in substances, the coexistence of high J_s and high GFA is difficult. Since this matter should be immensely important from academia to industry in the material field, a great deal of effort has been devoted; however, it has remained unsolved for many years. In this paper, we present a novel Fe-rich FeSiBP BMG with high J_s of 1.51 T comparable to the ordinary Fe–Si–B amorphous alloy now in practical use as well as with high GFA leading to a rod-shaped specimen of 2.5 mm in diameter, obtained by Cu-mold casting in air.     

Magnetic anisotropy of amorphous (Fe1−x Co x )78Si10B12 alloys

In order to better understand the problem of magnetic anisotropy in amorphous alloys produced by a rapidly quenching technique, in-plane magnetic anisotropy of amorphous (Fe_1−x Co _x (₇₈Si₁₀B₁₂ alloys was measured by means of a torque magnetometer using a disk specimen made from the amorphous alloy ribbon. The amorphous ribbons were prepared by a single roller type quenching apparatus. It was found that the anisotropy had mostly twofold symmetry in all the alloy cases, and that the concentrationx dependence of the anisotropy constant behaved differently from that of the magnetostriction. Moreover, the anisotropy did not disappear by subsequent annealing at high temperatures where the internal stress relief and the crystallization were completed.     

High frequency impedance of cobalt-based soft magnetic amorphous ribbons near the Curie temperature

The impact of FeNi magnetic conductive coating on the high frequency impedance of Co₆₄Fe₃Cr₃Si₁₅B₁₅ amorphous ribbons and its dependence on an external magnetic field’s strength and temperature is studied. It is shown that the coating affects the range of the magnetic field with the greatest change in the impedance of the external magnetic field, along with the temperature sensitivity of the impedance modulus and its components in the region of phase transition. The considerable differences between the properties of amorphous ribbons and CoFeCrSiB/FeNi composites found in this work allow us to evaluate the prospect of future studies aimed at developing magnetoimpedance elements for nonmarker biodetection.     

Properties of a rare earth free L10-FeNi hard magnet developed through annealing of FeNiPC amorphous ribbons

The rare-earth-free hard magnetic L1₀-FeNi phase found in cosmic meteorites demonstrates potential as a next-generation permanent magnet. However, it is very difficult to artificially produce the L1₀-FeNi phase due to the low atomic diffusion coefficients of Fe and Ni near the order-disorder transition temperature (∼320 °C). Therefore, FeNiPC amorphous alloy systems exhibiting crystallization temperature (T_x) near the transition temperature were investigated. The amorphous alloys were annealed at T_x, resulting in high atomic diffusion. The structural and microstructural characterizations of annealed ribbons revealed the formation of L1₀-FeNi phase through observation of the superlattice peak. The magnetic property, such as coercivity (H_c), also indicated the formation of L1₀-FeNi phase, because the maximum H_c value is 641 Oe after the annealing process.     

The existence of giant magnetocaloric effect and laminar structure in Fe73.5−xCrxSi13.5B9Nb3Cu1

Amorphous soft magnetic ribbons Fe_73.5−xCr_xSi_13.5B₉Nb₃Cu₁ (x=1–5) have been fabricated by rapid quenching on a single copper wheel. The differential scanning calorimetry (DSC) patterns showed that the crystallization temperature of α-Fe(Si) phase is ranging from 542 to 569 °C, a little higher than that of pure Finemet (x=0). With the same annealing regime, the crystallization volume fraction as well as the particle size of α-Fe(Si) crystallites decreased with increasing Cr amount substituted for Fe in studied samples. Especially, the interesting fact is that the laminar structure of heat-treated ribbons on the surface contacted to copper wheel in the fabricating process has been firstly discovered and explained to be related to the existence of Cr in studied samples. The hysteresis loop measurement indicated that there is the pinning of displacement of domain walls. The giant magnetocaloric effect (GMCE) has been found in amorphous state of the samples. After annealing, the soft magnetic properties of investigated nanocomposite materials are desirably improved.     

Investigation of magnetic properties and micromagnetic structure of multicomponent Fe61.4Ni3.6Cr3.2Si2.4Nb7.8Mn3.6B18 amorphous ribbons

The magnetic properties and micromagnetic structure (equilibrium distribution of magnetization) of multicomponent Fe_61.4Ni_3.6Cr_3.2Si_2.4Nb_7.8Mn_3.6B₁₈ amorphous ribbons are studied using scanning Kerr microscopy and a vibrating sample magnetometer. 5-mm-wide and 35-μm-thick ribbons were obtained by hardening of melt in a rapidly rotating drum. Strong difference in the surface and bulk magnetic parameters of the ribbons is established. Domain walls (DW) parallel to the ribbon length are detected. It is shown that quasistatic magnetization reversal of ribbons mainly occurs due to the DW displacement.     

FeCo基纳米晶合金高温交换耦合作用机理

研究了500和600℃真空退火后的纳米晶Fe_38.4Co₄₀Si₉B₉Nb_2.6Cu合金初始磁导率随温度的变化规律,发现较高温度(600℃)退火的FeCo基纳米晶合金,在非晶相居里温度以上较宽温度范围内磁导率没有明显的衰减,这是在双相纳米晶合金中观察到的一种新现象,其磁特性不同于Fe基纳米晶合金.为了探明这种现象的起源,估算了与剩余非晶相同成分的非晶合金的居里温度及纳米晶粒间发生交换耦合作用的参数 关键词： 交换耦合作用 非晶相居里温度 交换耦合穿透深度