Soft Magnetic Amorphous Ribbons Research Articles

Flexible Mini‐Inductors with Ultra‐High Inductance Density Directly Cut from Soft Magnetic Amorphous Alloys by Femtosecond Laser

AbstractInductors are indispensable parts in power modules of electronic devices. With the rapid development of flexible and wearable electronic devices, developing flexible micro‐inductors with large energy storage has become an urgent task. In this research, a sophisticated femtosecond laser ablation technique is employed to craft circular spiral mini‐inductors via selective etching of soft magnetic amorphous alloy ribbons. Remarkably, while these inductors possess dimensions akin to human fingerprints, they demonstrate an impressively elevated inductance value of ≈1.15 µH at 1 MHz. The inductance density is ≈280–390 nH mm−2, which is ≈10 times larger than conventional circular spiral inductors and is attributed to the high permeability of the amorphous alloys. Furthermore, the inductors showcase commendable flexibility, marked by stellar elasticity and a bending endurance exceeding 2500 cycles, thanks to the amorphous alloys' superior elastic strain limit. When integrated with an LM2576‐3.3BT buck converter, the fabricated inductor achieved a peak power conversion efficiency nearing 70%. These findings underscore the potential of such flexible mini‐inductors in the landscape of flexible electronics.

Laser punching of soft magnetic Fe-based amorphous ribbons

Soft-magnetic Fe-based amorphous materials are indispensable in electronic components. However, traditional processing methods (mechanical punching or wire cutting) degrade the amorphous structure, introduce stress, and are inefficient. To overcome these limitations, we introduce a precision processing technique for the Fe-based amorphous ribbons, namely laser punching. We compare two laser types: the picosecond pulse ultraviolet (PS-UV) laser, representing “cold” lasers, and the continuous-wave infrared (CW-IR) laser, epitomizing “hot” lasers. Our results demonstrate that the PS-UV laser can produce intricate geometries with minimal thermal or stress-induced effects. In contrast, the CW-IR laser induces nano-crystallization and crinkling due to heavy thermal effect. As an example, we successfully craft an amorphous motor stator using the PS-UV laser-processed ribbons, which exhibits considerably reduced iron losses compared to that fabricated with CW-IR laser. The reduction in iron loss and enhanced efficiency underscores the potential of PS-UV laser punching as a promising method for manufacturing amorphous motors.

Effect of domain size on the magneto-elastic damping in amorphous ferromagnetic metals

Abstract We show that the damping of longitudinal mechanical oscillations in soft magnetic amorphous ribbons can be significantly reduced by domain refinement. The latter is realized by an out-of-plane anisotropy induced by magnetic field annealing. The phenomena is interpreted in terms of micro eddy currents associated with the magnetization process within a domain.

Outstanding magnetocaloric properties at ambient temperature of a Fe88La4Ce3B5 amorphous alloy

Fe88La4Ce3B5 amorphous alloy was successfully vitrified in the shape of ribbon with an average thickness of 39 micrometer. The magnetic and magnetocaloric properties of the Fe88La4Ce3B5 metallic glass were investigated. It was found that the soft magnetic amorphous ribbon exhibits a high peak value of magnetic entropy change (3.93 J/(K × kg) at 302.5 K under 5 T), which is higher than those of other iron-based metallic glasses. The outstanding magnetocaloric properties of the Fe88La4Ce3B5, give rise to a new way to improve the magnetocaloric properties around room temperature in the iron-based metallic glasses by adding RE elements.

Effect of Substituting Hf for Zr on Fe-Co-M-Nb-B (M = Zr, Hf) Amorphous Alloys with High Saturation Magnetization

The soft magnetic amorphous ribbons of (FexCo1−x)85M9Nb1B5 (M = Zr or Hf, x = 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9) were investigated in this study. Replacing Zr by Hf turned out to increase saturation magnetization and, at the same time, reduce the coercivity, both of which serve together in enhancing the soft magnetic performance of the alloys. Moreover, the optimum ratio of Fe/Co was determined after the survey on different alloys with varying Fe/Co ratio resulting in the maximum saturation magnetization while keeping the coercivity low. After optimization, the highest saturation magnetization of 1.62 T was achieved with coercivity of 11 A/m. While substitution of Hf for Zr slightly reduced the crystallization onset temperature of the amorphous structure, the thermal stability of the soft magnetic amorphous alloys was not significantly affected by the Zr/Hf replacement.

Stress Dependence of the Small Angle Magnetization Rotation Signal in Commercial Amorphous Ribbons.

The results of the investigation on tensile stress dependence of the SAMR (small angle magnetization rotation) signal in soft magnetic amorphous ribbons are presented. Exemplary results for commercially available, negatively magnetostrictive 2705M, 2714A, and 6030D amorphous ribbons show significant stress dependence, in contrast to positively magnetostrictive 2826MB alloy. The magnetoelastic hysteresis of the obtained characteristics is compared, as well as the influence of the biasing H field and supply current variations. Based on the results, 2705M alloy with near-zero negative magnetostriction is proposed as best suited for a SAMR-based, magnetoelastic force sensor.

Significant improvement of soft magnetic properties for Fe-based nanocrystalline alloys by inhibiting surface crystallization via a magnetic field assisted melt-spinning process

Abstract Fe-based soft-magnetic amorphous and nanocrystalline ribbons made with a single-side fast-cooling process always suffer from the surface crystallization which deteriorates the magnetic properties and inhibits the wide applications. In this study, a static magnetic field assisted melt-spinning process was employed to prepare the typical Fe84.75Si2B9P3C0.5Cu0.75 alloy ribbon with an attractive application prospect. According to the comparative investigations of the crystallization behavior, structural evolution process and magnetic properties, it is found that the applied magnetic field can effectively inhibit the formation of compound phases and decrease the size of textured α-Fe grains in the surface layer of the as-spun ribbon. The Fe84.75Si2B9P3C0.5Cu0.75 samples made with low purity raw materials and under an optimal field exhibit superior magnetic properties, including a high saturation magnetization (Bs) over 1.82 T, low coercivity (Hc) of 8.5 A/m, high permeability (μ) of 2.76 × 104 at 1 kHz and much lower losses, after nanocrystallization by annealing. The apparent effect of the applied magnetic field was discussed from the disturbance of a Lorentz force of the fast-moving molten alloy and a magnetic force of preformed grains in a magnetic field during the melt-spinning process. These results provide a novel solution of surface crystallization and an effective route for improving magnetic properties of Fe-based amorphous and nanocrystalline alloy ribbons.

Fabrication and soft magnetic properties of rapidly quenched Co-Fe-B-Si-Nb ultra-thin amorphous ribbons

Abstract Ultra-thin soft magnetic amorphous ribbons of Co-Fe-B-Si-Nb alloy were synthesised by a single step rapid-quenching approach to acquire advantage of improved material performance and lower costs over commercial amorphous alloys. The amorphous ribbons of approximately 5.5 µm thicknesses were quenched by a single roller melt spinner in a single-step production process and characterised for their structural and magnetic properties. The disordered atomic structure of amorphous ribbons was confirmed by the X-ray diffraction. A surface morphology study revealed the continuity of ultra-thin ribbons without pores over a large scale. The amorphous alloy showed the ultra-soft magnetic properties in the as-quenched state. The observed thickness dependency of the magnetic properties was attributed to the increased surface roughness and possibly due to a lack of densely packed atomic structure resulting from the extremely high cooling rates experienced by ultra-thin ribbons. We propose that in-situ thinning process of amorphous ribbons significantly reduces the basic material cost and eliminates the need for post-processing steps; hence it provides the opportunity for mass production of high-performance soft magnetic amorphous ribbons at relatively lower costs.

Unusual flow behavior of Fe-based soft magnetic amorphous ribbons under high temperature tensile loading

The viscous thermal flow behavior and mechanical property of [Fe0.6Co0.15B0.2Si0.05] (100−x)Tax (x = 0, 1, 2, 3, 4, and 5) soft magnetic amorphous ribbons were studied. The characteristics of melt-spun amorphous ribbons were measured by using vibration sample magnetometer (VSM), nanoindentation, differential scanning calorimetry (DSC) and thermo-mechanical analysis (TMA) to study the effects of Ta content variation on the thermal stability, mechanical, and soft magnetic properties. We observed that the nanoindentation hardness, Young's modulus, and glass transition and crystallization temperatures were improved by the addition of Ta. Using dilatometry measurement, TMA, by heating at a constant rate under tension mode, we examined not only the glass transition and crystallization behaviors but also the possibility of coexistence of multiple amorphous phases.

Using finite element modelling and experimental methods to investigate planar coil sensor topologies for inductive measurement of displacement

The usage of planar sensors is widespread due to their non-contact nature and small size profiles, however only a few basic design types are generally considered. In order to develop planar coil designs we have performed extensive finite element modelling (FEM) and experimentation to understand the performance of different planar sensor topologies when used in inductive sensing. We have applied this approach to develop a novel displacement sensor. Models of different topologies with varying pitch values have been analysed using the ANSYS Maxwell FEM package, furthermore the models incorporated a movable soft magnetic amorphous ribbon element. The different models used in the FEM were then constructed and experimentally tested with topologies that included mesh, meander, square coil, and circular coil configurations. The sensors were used to detect the displacement of the amorphous ribbon. A LabView program controlled both the displacement stage and the impedance analyser, the latter capturing the varying inductance values with ribbon displacement. There was good correlation between the FEM models and the experimental data confirming that the methodology described here offers an effective way for developing planar coil based sensors with improved performance.

Magnetization distribution in a soft magnetic amorphous alloy ribbon in as-quenched state and efficiency of heat treatment

The effect of heat treatment in air on the formation of magnetic properties has been studied based on the example of soft magnetic Fe77Ni1Si9B13 and Fe81B13Si4C2 amorphous ribbons characterized by positive magneto-striction. The magnetization distribution in the ribbons in the as-quenched state was shown to affect the efficiency of annealing. Under certain conditions, heat treatment, which results in the formation of mainly amorphous state of ribbon surface, is more efficient for samples characterized by high volume of orthogonally magnetized domains. This can be related to high in-plane tensile stresses, which are induced by hydrogen and oxygen atoms introduced into the ribbon surface upon its interaction with atmospheric water vapor.

Joule heating scanning structure system.

A method and its system to study the structural evolution on soft magnetic amorphous and nanocrystalline ribbon shaped alloys are presented. With only one sample, a complete set of magnetic and electric data at room and at high temperature are obtained in a relatively short period of time, allowing us to elucidate the structural changes occurring in the alloy and to determine the optimal soft magnetic properties annealing conditions.

Asymmetric magnetoimpedance effect in CoFeSiB amorphous ribbons by combination of field and current annealing for sensor applications

The roles of applied magnetic field during the current annealing of Co68.15Fe4.35Si12.5B15 soft magnetic amorphous ribbons are studied. Samples heat treated by Joule heating effect in open air and simultaneously in the present of longitudinal external magnetic field showed asymmetric magnetoimpedance (AMI) behavior. The AMI profile can be related to the exchange bias interaction between the soft magnetic amorphous material and a harder magnetic crystalline phase formed on the surface of the ribbon. This effect stems from thermal effect, the transverse Oe field generated from the annealing current which is thickness dependent and the longitudinal external field. The single peak AMI with the field sensitivity of 101%/Oe for DC annealing current is achieved. Our results could address a simple way to achieve the AMI response toward developing high sensitive magnetic field sensors.

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.

Soft magnetic properties of Fe(87−x)Ti7Zr6[B x Si x ]0.5 amorphous metallic ribbons prepared by melt-spinning

The soft magnetic Fe-based amorphous metallic ribbons Fe(87−x)Ti7Zr6[BxSix]0.5 (x = 8, 10, 12%) were prepared using the melt-spinning technique to have thickness of 15–22 μm and widths of 1-2 mm. Increasing the amounts of B and Si improved the soft magnetic properties: the coercivity (Hc) decreased, and the saturation magnetization (MS) increased, the thermal and structural properties remained the same. Due to the high sensitivity of the alloys to the process conditions, variations in the widths of the melt-spun ribbons induced structural modifications, resulting in significant change in the soft magnetic properties. While the ribbons made with 1 mm widths had fully amorphous structures and soft magnetic properties, the ribbons with 2 mm widths showed semi-hard magnetic properties, which was attributed to the formation of nanocrystals inside the amorphous structures.

Structure Design and Properties of Amorphous Filter Reactors

Five filter reactors as tools for higher harmonics suppression in the power system were fabricated with Fe based soft magnetic amorphous ribbons. The fabrication processes that combine amorphous core winding, heat treatment, dipping, drying, cutting, and assembling were performed to obtain low core loss amorphous reactors. The properties of the reactors are investigated in detail in this article. Experiments results indicate that the core losses of the amorphous reactor cores are far lower than that of silicon steel reactors cores. At the same time, the core temperature rises of the amorphous reactors are also smaller and the noise levels of the reactors accord to the requirement for sale. Altogether, the Fe-based amorphous ribbons can be successfully used to fabricate low loss reactor cores.

Highly zero-biased magnetoelectric response in magnetostrictive/piezoelectric composite

The magnetoelectric (ME) coupling is investigated in laminated composites employing piezoelectric ceramic PZT (PZT-8), iron-nickel-based ferromagnetic alloy with constant elasticity (FeNi-FACE), and soft magnetic amorphous ribbon FeCuNbSiB (Fe73.5Cu1Nb3Si13.5B9). The two different ferromagnetic materials of FeNi-FACE and FeCuNbSiB result in built-in dc magnetic bias (Hdc) due to difference in their magnetic permeability and coercivity. In addition, the relatively high mechanical quality factors (Qm) for FeNi-FACE, PZT-8, and FeCuNbSiB enhance the resonant ME voltage due to an increased effective Qm of ME composite. Hence, a strong resonant ME response at zero-biased dc magnetic field can be obtained. The corresponding ME voltage coefficients (MEVC) at resonance for PZT/FeNi-FACE/FeCuNbSiB (FeFP) composite and FeCuNbSiB/FeNi-FACE/PZT/FeNi-FACE/FeCuNbSiB (FeFPFFe) composites achieve 2.19 V/Oe (27.375 V/cm Oe) and 3.37 V/Oe (42.125 V/cm Oe), respectively, which is ∼102 times higher than that of the previously reported NKNLS-NZF/Ni/NKNLS-NZF trilayer composite.

Continuous-annealing method for producing a flexible, curved, soft magnetic amorphous alloy ribbon

A method has been developed for continuous annealing of an amorphous alloy ribbon moving forward at several meters per second, giving a curved shape to the ribbon that remains flexible afterward and can be easily wound into a toroidal core with excellent soft magnetic properties. A heat pulse was applied by a compact system on a Metglas 2605HB1 ribbon moving forward at 5 m/s to initiate a thermal treatment at 460 °C, near crystallization onset. The treatment duration was less than 0.1 s, and the heating and cooling rates were above 10 000 °C/s, which helped preserve most of the alloy as-cast ductility state. Such high temperature rates were achieved by forcing a static contact between the moving ribbon and a temperature-controlled roller. A tensile stress and a series of bending configurations were applied on the moving ribbon during the treatment to induce the development of magnetic anisotropy and to obtain the desired natural curvature radius. The core losses at 60 Hz of a toroidal test core wound with the resulting ribbon are lower than the specific values reported by the alloy manufacturer. This method can be implemented at the casting plant for supplying a low-cost, ready-to-use ribbon, easy to handle and cut, for mass production of toroidal cores for distribution transformer kernels (core and coil only), pulse power cores, etc.

Hysteretic giant magnetoimpedance effect analyzed by first-order reversal curves

We applied the first-order reversal curve method to hysteretic giant magnetoimpedance (GMI) of soft magnetic amorphous ribbons with a well-defined transversal domain structure and quasi-anhysteretic magnetization behavior. In opposition to major curve, it gives access to the distribution of local irreversible changes of the transverse permeability, which undergo a gradual transition. Results show that hysteretic GMI effect consists of three distinct regimes depending on the applied field. An interlinked hysteron/anti-hysteron model is proposed to analyze the obtained results, which allows one to follow the influence of frequency and anisotropy upon the irreversible switches probed by GMI.

Time of isothermal holding in the course of in-air heat treatment of soft magnetic Fe-based amorphous alloys and their magnetic properties

On the example of soft magnetic Fe81B13Si4C2 and Fe77Ni1Si9B13 amorphous alloys, the relation between the level of magnetic properties and duration of isothermal holding in the course of heat treatment in air has been studied. The optimum temperature-dependent time τ of isothermal holding has been shown to be related to the volume fraction of domains (Vorth) with orthogonal magnetization in the initial (quenched) ribbon by equation Vorth = ττ1/3. A temperature dependence of the proportionality coefficient α, which determines the degree of diffusion-process activity, has been determined. The results obtained allow us to substantially simplify the choice of optimum conditions of atmospheric heat treatment of soft magnetic Fe-based amorphous ribbons.