Good Soft Magnetic Properties Research Articles

The origin of good mechanical and soft magnetic properties in a CoFeNi-based high-entropy alloy with hierarchical structure

With the industry development, materials that combine good mechanical properties with new functional applications are in high demand. Here, a solution was provided to overcome low mechanical properties of soft magnetic materials through heterostructure design in CoFeNi high-entropy alloys (HEA). A CoFeNi-based HEA with a hierarchical structure with heterogeneous microstructure, consisting of body-centered cubic (BCC) bands, ultra-fine grained dual-phase and non-recrystallized lamellae (NRL) zones containing a high-density of nanoprecipitates, was fabricated and finely tuned by cold rolling (CR) and annealing. The HEA annealed at 850 °C (HEA-850) exhibits a noteworthy strength-ductility synergy than the counterparts with homogeneous dual-phase microstructures. The yield strength and elongation of the HEA-850 sample are nearly up to 1 GPa and 24%, respectively. Furthermore, because of the elimination of high-density dislocations, this alloy possesses good soft magnetic characteristics, and the saturation magnetization (Ms) and coercivity are 120 emu/g and 455 A/m, respectively. Detailed microstructure observations reveal that the high yield strength is mainly attributed to the interphase boundary strengthening from the dual-phase ultra-fine regions and nanoprecipitate strengthening as well as dislocation strengthening from NRL regions. Due to the mechanical and microstructural heterogeneity, multiple hetero-deformation induced hardening sustains persistent work hardening during tensile deformation, resulting in the reasonable ductility in the HEA-850 sample. The novel provides an important insight into developing high-performance materials with a superior combination of mechanical and functional properties using heterogeneous microstructure.

Microstructure and magnetic properties of Nanomet compacted by spark plasma sintering

Nanocrystalline soft magnetic materials with high saturation polarization and low losses have a high potential in motor applications. Thus, toroidal cores were compacted by spark plasma sintering of flakes of the melt-spun Nanomet alloy Fe-Si-B-P-Cu. The thermal properties of the ribbons were analyzed by DSC to determine the crystallization temperatures. The influence of the initial powder and of the compacting parameters such as maximum temperature and dwell time on the density and the magnetic properties in DC and AC were investigated. An optimum temperature range of approximately 50 K was determined for good soft magnetic properties. An effect of the dwell time was not recognized in the observed range. By compacting flakes of different sizes, the maximum permeability can be adjusted in the range of up to 7000. The microstructure was observed by means of XRD and TEM in order to confirm the amorphous and nanocrystalline state, respectively. Using the Lorenz mode of the TEM, it was possible to calculate the magnetic domain wall width for the samples and compare the resulting calculated magnetic properties with the experiments.

Effect of sodium gluconate addition on anomalous codeposition of electroplated nickel-iron alloys

Invar nickel-iron alloy has been widely applied in the fields of electronics, sensors, communications and optics, due to its low thermal expansion coefficient, high hardness, high ductility and other characteristics according to product requirements. The application in metal stencil during the manufacturing process of active-matrix organic light-emitting diodes is mainly due to their good electrical conductivity and soft magnetic properties. In this study, sodium gluconate is used as a substitute for boric acid in the acidic electroplating of nickel-iron alloys; the concentration ratio of nickel-iron in the plating bath is 2:1. After adding sodium gluconate, the precipitation of nickel varies significantly. The iron content in the weight percentage of the deposited nickel-iron alloy is obviously larger than nickel, even up to 3 times. The whole deposition process is in the state of anomalous codeposition, and the selectivity ratio reaches 3 or more; the nickel-iron alloy deposited by adding sodium gluconate to the plating bath has a great influence on the material properties of the nickel-iron alloy plating, The nickel-iron alloy deposited at -1.4 V exhibits a hardness of approximately 3.17 GPa and a modulus of elasticity about 37.88 GPa. Notably, the resistance to plastic deformation of the alloy deposited in sodium gluconate plating solution (H3/U2=0.022) is significantly higher than that in boric acid plating solution (H3/U2=0.007). The experimental results also show that it has the best ability to resist plastic deformation.

Effect of Bi2O3-CuO Flux on the Microstructure, Soft Magnetic Properties, and Gyromagnetic Properties of NiCuZn Ferrites for LTCC Devices.

In this work, the electromagnetic properties of Ni0.22Cu0.31Zn0.47Fe2O4 (NiCuZn) ferrites doped with 0.3 wt% Bi2O3 + xCuO flux (x = 0.2, 0.4, 0.6, and 0.8 wt%) were studied. Doping resulted in a reduction in the sintering temperature to 900 °C. The doped ferrites were synthesized via the solid-state method. XRD patterns revealed that the prepared ferrites had a cubic spinel structure; thus, a moderate addition of flux did not change the crystal structure. The SEM images, as well as the density and grain size distribution of the samples, showed that the NiCuZn ferrites had densified, homogenized, and contained fully grown grains for x = 0.6 wt%. The sample exhibited good soft magnetic properties, with μ' reaching the maximum value of 245.4 for x = 0.6 wt% and ε', Ms, and Hc reaching the maximum values of 23.1, 28.06 emu/g, and 45.86 Oe for x = 0.8 wt%, respectively. Furthermore, the ferrites exhibited good gyromagnetic properties, with 4πMs reaching the maximum value of 1744 Gauss for x = 0.8 wt% and ΔH reaching the minimum value of 228 Oe for x = 0.6 wt%. NiCuZn ferrites were successfully sintered at a lower temperature (900 °C) by adding Bi2O3-CuO flux through LTCC technology and exhibited good soft magnetic properties and gyromagnetic properties. We envisage that these ferrites could be used in multilayer devices.

Magnetic properties of an Fe-based amorphous soft magnetic composite prepared via in-situ steam oxidation

Reducing the core losses of motors and transformers is an important way to address the global environment and energy resource problems. Soft magnetic composites (SMCs) comprising of electrically insulated ferromagnetic powder has shown vast potential for applications at low to high applied frequencies. In this work, in-situ steam oxidation was used to coat the surface of amorphous Fe75.5Si4B6P8C6Mo0.5 powder with an insulating layer. The thickness and composition of the Fe-oxide layer were controlled by tuning the in-situ steam oxidation time, and more cracks and Fe2+ were formed on the powder surface with the extension of oxidation time. The magnetic Fe-oxide layer of amorphous powder not only plays an insulating role to reduce the Pe, but also affects the magnetic coupling of particles that leads to the change of Ph. And the amorphous SMCs with 10 h in-situ steam oxidation treatment exhibits good comprehensive soft magnetic properties, i.e., the magnetic loss (Pcv), effective permeability (μe) and DC bias are 61.44 W/kg (50 mT, 100 kHz), 30.4 (to 10 MHz) and 71.5% (100 Oe), respectively.

Analysis of icosahedral structure in rapidly solidified Pd<sub>82</sub>Si<sub>18</sub> amorphous alloy under high pressure

Compared with traditional glass, metallic glass (MG) has excellent properties, such as high strength, high hardness, high fracture toughness, good soft magnetic properties and corrosion resistance due to its unique structure. Such properties enable it to be used in optics, electronics, construction and other fields, making it a highly promising new material with great application potential. As the properties of amorphous alloys are closely linked with their local structures, microstructure characteristics have always been a research focus in the amorphous field. Previous studies show that the onset temperature of heredity and the hereditary fraction of characteristic clusters can be used to effectively evaluate the glass-forming ability. In order to obtain the relationship between the microstructure characteristic and cluster evolution of amorphous alloy, and reveal the formation of glass, the glass transition processes of the Pd<sub>82</sub>Si<sub>18</sub> alloy under different pressure conditions are simulated by using the molecular dynamics method, and the heredity and evolution of the Pd<sub>82</sub>Si<sub>18</sub> amorphous alloy are analyzed by using the cluster-type index method and the reverse tracking method. The simulation results show that the glass transition temperature of the Pd<sub>82</sub>Si<sub>18</sub> alloy can be increased when the pressure is higher, and a large number of icosahedra are formed in the solidified alloy when the pressure is sufficiently high. Icosahedron is a kind of structure that widely exists in amorphous materials and has been studied for quite a long time. In this work, a detailed comparative analysis of two icosahedra is conducted and the heritability of clusters with different chemical compositions under high pressure is studied. The results show that it is easier for icosahedra with central atom Pd and those with central atom Si to form a medium-range order in the Pd<sub>82</sub>Si<sub>18</sub> amorphous alloy. An increase in pressure conduces to the increase of both onset temperature of heredity and hereditary fraction. Combined with the results of cluster heredity analysis at 0 GPa, the Si-centered clusters have stronger heritability than Pd-centered clusters, thus the former ones have a greater influence on the glass-forming ability. These findings are of significance in understanding the relationship between microstructure evolution and glass formation, and also providing certain guidance for designing amorphous alloys.

Analysis of icosahedral structure in rapidly solidified Pd<sub>82</sub>Si<sub>18</sub> amorphous alloy under high pressure

Compared with traditional glass, metallic glass (MG) has excellent properties, such as high strength, high hardness, high fracture toughness, good soft magnetic properties and corrosion resistance due to its unique structure. Such properties enable it to be used in optics, electronics, construction and other fields, making it a highly promising new material with great application potential. As the properties of amorphous alloys are closely linked with their local structures, microstructure characteristics have always been a research focus in the amorphous field. Previous studies show that the onset temperature of heredity and hereditary fraction of characteristic clusters can be used to effectively evaluate the ability of an amorphous alloy to form glass. In order to obtain the relationship between the microstructure characteristic and cluster evolution of amorphous alloy, and reveal the formation of glass, the glass transition processes of the Pd<sub>82</sub>Si<sub>18</sub> alloy under different pressure conditions are simulated by using the molecular dynamics method, and the heredity and evolution of the Pd<sub>82</sub>Si<sub>18</sub> amorphous alloy are analyzed by using the cluster-type index method and the reverse tracking method. The simulation results show that the glass transition temperature of the Pd<sub>82</sub>Si<sub>18</sub> alloy can be increased when the pressure is higher, and a large number of icosahedra are formed in the solidified alloy when the pressure is sufficiently high. Icosahedron is a kind of structure that widely exists in amorphous materials and has been studied for quite a long time. In this work, a detailed comparative analysis on two icosahedra is conducted and the heritability of clusters with different chemical compositions under high pressure is studied. The results show that it is easier for icosahedra with central atom Pd and those with central atom Si to form a medium-range order in the Pd<sub>82</sub>Si<sub>18</sub> amorphous alloy. An increase in pressure conduces to the increasing of both onset temperature of heredity and hereditary fraction. Comparing with the results of cluster heredity analysis under 0 GPa, the Si-centered clusters have stronger heritability than Pd-centered clusters, thus the former ones have a greater influence on the ability to form glass. These findings are of significance in understanding the relationship between microstructure evolution and glass formation,and also providing certain guidance for designing amorphous alloys.

Effect of Mn content on crystallization behaviors and magnetic properties of FeCoNiBMn high-entropy amorphous alloys

FeCoNi-based high-entropy alloys (HEAAs) attracted much attention because of their good thermodynamic stability, mechanical properties and soft magnetic properties. In this paper, Fe22Co22Ni22B34-xMnx (x = 6–22 at%) HEAAs were designed and the effects of Mn on the crystallization behaviors, magnetic performance, and mechanical property were investigated. The crystallization behaviors of the FeCoNiBMn HEAAs are: 1) 12–16 at% Mn: am → am’ + M23B6 → M23B6 + fcc; 2) 18 at% Mn: am → am’ + bcc + M23B6 → bcc + M23B6 → fcc + M23B6; and 3) 20–22 at% Mn: am → am’ + bcc → bcc + M23B6 → fcc + M23B6. Two parameters ΩA and VEC are proposed to predict the primary precipitates of FeCoNi-based HEAAs. All as-spun ribbons exhibit excellent soft magnetic properties with a very low coercivity (Hc) of less than 1.5 A/m and a maximum saturation magnetization (Bs) of 0.82 T. The 14 at% Mn alloy exhibits very low Hc of less than 4 A/m even after complete crystallization. Magnetic properties and Vickers hardness of crystalline ribbons are closely related to crystallization behaviors.

THE POWDER OF Co64Nb30B6 OBTAINED BY MECHANICAL ALLOYING

This work aims to synthesize the alloy Co64Nb30B6 through mechanical alloying using a planetary ball mill. A disc rotation per minute and a ball/powder weight ratio of 300 rpm and 10:1 were used, with a milled time of 10 h, respectively. The characterization of the Co64Nb30B6 alloy was performed by X-ray diffraction (XRD), examined by scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS), thermoanalytical techniques (TGA/DTA), vibrating sample magnetometer (VSM) and confirmed by Braunauer, Emmet e Teller (BET) method type IV isotherms with a hysteresis loop for mesoporous materials. The results indicated that the evolution of the amorphous phase in the Co64Nb30B6 composition through the mechanical alloying process exhibited good soft magnetic properties with the addition of the metalloid element B and its excellent unique ferromagnetic properties. Through thermoanalytical analysis (TGA/DTA), it was shown that at higher temperatures, Co and Nb ions are oxidized by the environment and, therefore, the mass can be slightly increased to 14.9% and a probable contribution of boron in evolution stability thermal and magnetic in the amorphous phase, respectively. This suggests that the newly developed high-performance amorphous alloy Co64Nb30B6 has great application potential.

Formation of cube-on-face texture {0 0 1}〈uv0〉 in a high saturation soft magnetic iron-cobalt-vanadium alloy by controlled phase-transformation γ → α

In this investigation, the soft magnetic properties of a high saturation iron-cobalt-vanadium alloy with 17 wt% Co and 1.5 wt% V have been greatly enhanced by a special heat treatment in the γ-region, which effectively leads to the formation of a magnetically favorable strong cube-on-face texture during cooling. Based on EBSD analyses, a high degree of cube-on-face texture {001}〈uv0〉 of up to 80 % was obtained. The underlying mechanism is presumed to be a preferred surface nucleation of {001}-grains during cooling through the two-phase-region α + γ. The annealing of all samples was performed in ceramic powder. Therefore, mechanical stress is not considered the primary cause for this preferred nucleation, which should simplify the upscaling to an industrial process. As the 〈100〉 direction is the magnetic easy axis in this material system, this preferred crystal orientation goes along with very good soft magnetic properties such as a high maximum permeability µmax of 16,000, an increased induction B(160 A/cm) of 2.14 T and a reduced coercivity Hc of about 30 A/m. The core loss is reduced for frequencies up to 1 kHz. This favorable combination of properties, along with the reduced Co content, opens up new possibilities for the use of this material in electrical machines with both a high efficiency and a high power density.

Comparing the formation, properties and structure between Fe20Co20Ni20Cr20(P0.45B0.2C0.35)20 high-entropy metallic glass and the predecessor Fe75Cr5P9B4C7 metallic glass

In present work, formation, properties and local structure features between novel Fe20Co20Ni20Cr20(P0.45B0.2C0.35)20 high-entropy metallic glass (HEMG) and the predecessor Fe75Cr5P9B4C7 metallic glass (MG) were thoroughly characterized by experiments and ab-initio molecular dynamics (AIMD) simulation. Compared with predecessor MG, the HEMG possesses a higher thermal stability of supercooled liquid with wider supercooled liquid region of 57 K, superior corrosion resistance with higher corrosion potential, lower corrosion and passive current density along with wider passive region in 3 wt.% NaCl solution. Additionally, the HEMG possesses a paramagnetic feature with low magnetization of only 9.38 emu·g−1, while predecessor MG possesses a good soft-magnetic property with a high saturation magnetization of 115.16 emu·g−1. The corresponding local structure differences deriving from AIMD simulation exhibit that the HEMG possesses a higher content of icosahedra-like structures (with bond pair indexes (BPIs) of 1551, 1541 and 1431) and Voronoi polyhedra (VPs) with relative smaller coordination numbers (8, 9, 11, 12 and 13), lower content of crystal-type structures (with BPIs of 1421, 1422, 1441 and 1661) and VPs with larger coordination numbers (15 and 16) compared with predecessor MG. These results show that the formation, properties and local structures can be visibly changed after present high-entropy alloying by similar solvent elements Co, Ni and Cr equiatomic substitution of Fe in predecessor MG. Additionally, both alloys possess dominant VPs with coordination numbers from 12 to 15 and good ductility without fracture as bent by 180°.

Effects and mechanisms of Nb and Fe additions on glass-forming ability and magnetic properties of a Co71.5Gd3.5B25 metallic glass

Aiming to unraveling the effects and mechanisms of Nb and Fe additions on glass-forming ability (GFA) and magnetic properties, especially coercivity (Hc) on Co-based metallic glasses, 2–4 at% Nb and/or 7.15–28.6 at% Fe have been alloyed into a Co71.5Gd3.5B25 alloy by substitution of Co. The results show that alloying either Nb or Fe into the base alloy leads to enhanced stability of supercooled liquid and GFA, and bulk metallic glass (BMG) can be formed for the alloy with 4 at% Nb or 28.6 at% Fe. Combined addition of Nb and Fe further improves the thermal stability and GFA, and lowers viscosity in supercooled liquid state. A (Co0.6Fe0.4)67.5Gd3.5Nb4B25 BMG possess a wide supercooled liquid region (ΔTx) of 85 K, critical sample diameter of 3.0 mm, and minimum viscosity coefficient of 2 × 108 Pa∙s. The enrichment of Fe increases saturation magnetic flux density (Bs), Hc, and saturation magnetostriction coefficient (λs) of the (Co, Fe)-Gd-B-(Nb) metallic glasses; the addition of Nb effectively inhibits the deterioration of magnetic softness caused by Fe while reducing the Bs. The (Co0.6–0.9Fe0.1–0.4)67.5Gd3.5Nb4B25 BMGs possess good soft magnetic properties with the Bs and Hc ranging 0.43–0.69 T and 2.3–5.0 A/m, respectively. Ab initio molecular dynamics simulations indicated that alloying Fe into the Co-based metallic glasses leads to enhanced magnetic anisotropy energy. The increased magnetic anisotropy arising from enlarged λs results in the increased Hc. The combination of high GFA, large ΔTx, low viscosity, and good soft magnetic properties makes the Co-based Co-Fe-Gd-Nb-B BMGs highly promising for applications as micro electromagnetic devices produced through thermoplastic forming.

Influence of energy density on the microstructure, growth orientation, and anisotropy of magnetic properties in additively manufactured Fe-3.8wt%Si transformer steels

Fe-3.8wt%Si transformer steels were processed using two different additive manufacturing (AM) techniques, laser powder bed fusion (LPBF) and directed energy deposition (DED). While the LPBF processed samples exhibited a strong <001> orientation of the BCC grains along the build axis, the DED processed samples exhibited a randomized texture along the build axis. DED processed samples showed substantially coarser columnar grains as compared to their LPBF counterparts. The columnar grains exhibited a substantial number of low-angle sub-grain boundaries. All samples exhibited very good soft magnetic properties, with saturation magnetization (Ms) values ranging from 205 - 232 emu/gm, and coercivity (Hc) values ranging from 1.2 – 4.2 Oe. The Coercivity (Hc) values were significantly lower when the magnetic field was applied parallel to the build axis, as compared to being perpendicular, which can be rationalized based on the columnar nature of the grains, resulting in a higher number density of grain boundaries in case of the field applied perpendicular to the build axis.

Fabrication and excellent performance of amorphous FeSiBCCr/organic-inorganic hybrid powder core

Soft magnetic composites (SMCs) are widely used in relevant inductance components in power and electronic fields. The development of high frequency devices requires SMCs to exhibit good insulation and excellent soft magnetic properties. The insulation coating for SMCs is crucial, and it is necessary to ensure that the coating thickness is uniform and maintains excellent adhesion to the powder. In the present work, a novel and efficient solution for the formation of insulating coatings, i.e. phytic acid/silane (denoted as PAS) organic-inorganic hybrid solution, was prepared by the condensation reaction between PA and γ-(2,3-epoxypropoxy) propyl trimethoxy silane. The FeSiBCCr@PAS powder with a core-shell structure has been successfully prepared through chemical reaction in a modified PAS solution. The effects of insulating coating content on the magnetic and mechanical properties of FeSiBCCr@PAS powder cores were systematically investigated. The PAS hybrid insulating coating can significantly improve the DC-bias performance and reduce the core loss. The optiomal powder core, which was prepared by using the powder coated with 3 g/L phytic acid, exhibits a minimum core loss (P50mT/1MHz) of 2979.2 mW/cm3, high effective permeability μe(0.1A/m) of 33.8, and superior DC-bias(100Oe) performance of 80.8%. Present work developed an effective method to prepare high performance powder cores with good soft magnetic and mechanical properties.

Improved ductility of annealed Fe-based metallic glass with good soft magnetic property by cryogenic thermal cycling

The brittleness after annealing treatment severely restricts the subsequent processing and application of Fe-based magnetic metallic glass. Through proper annealing treatment combined with cryogenic thermal cycling, we obtained excellent comprehensive properties of Fe-based metallic glass ribbons with not only good soft magnetic properties but also high bending deformation ability. After thermal cycling, the sample rejuvenated with higher energy state and larger size of soft regions, which facilitated the initiation and branching of shear bands, leading to the improvement of bending plasticity. Although the large soft regions may act as pining sites for domain walls, the domain structure and coercivity of the sample remained nearly identical because of the reduced number of crystal-like structures. Our study indicates that the cryogenic thermal cycling is an effective method to regulate mechanical and magnetic properties, which makes it powerful means to obtain excellent performance of Fe-based magnetic metallic glasses.

Annealing Effect in Amorphous Fe-Co-B-Si-Nb According to Fe/Co Ratio

These days, electric motor qualities and energy-saving problems are significant to our society. The critical component of these problems is related to magnetic materials. In this respect, here, we investigated the (FexCo1−x)72B19.2Si4.8Nb4 (0 ≤ x ≤ 1, at 0.1 intervals) ribbon alloys’ structural, thermal, and magnetic properties. Replacing Co with Fe turned out to increase saturation magnetization up to 127.7 emu/g and improve thermal stability. Additionally, we conducted heat treatment at 843, 893, and 943 K for 10 mins, and the annealing effect in the amorphous (FexCo1−x)72B19.2Si4.8Nb4 (0.4 ≤ x ≤ 0.9, at 0.1 intervals) ribbons on structural and magnetic properties are analyzed. The saturated magnetization (Ms) value has increased by about 20 to 30 emu/g by the heat treatment and tends to increase as the annealing temperature increases until the annealing temperature approaches 893 K. After annealing at 943 K for 10 mins, the highest saturation magnetization of 156.8 emu/g was achieved. In addition, all four samples show the same coercivity trend. The coercivity decreases when the initial heat treatment at 843 K is applied to the ribbons. However, after annealing at this high temperature, such as 893, 943 K, the Fe3B, and (Fe, Co)23B6 phases are also generated and cancel out the good soft magnetic properties of α-(Fe, Co) phase.

Single-Step Synthesis of Nanocrystalline Fe-Ni/Fe-Co-Ni Magnetic Alloy Coating via Directional Plasma Spray

Fe-Ni-based nanocrystalline coatings with unique magnetic properties are widely used as soft magnetic materials and usually act as the core component in electronic devices. Nanocrystallized particles and thin films have become a popular contemporary research direction. Electrical explosion, characterized by an ultrafast atomization and quenching rate (dT/dt ~ 109-1011 K/s) for the material, is a unique approach for the rapid "single-step" synthesis of nanomaterials and coatings. In this study, experiments were carried out with intertwined wire under a directional spraying device in atmospheric Ar ambience. Two load systems of Fe-Ni and Fe-Ni-Co were considered in this work. Electrical parameters and high-speed camera images were obtained to reveal the physical mechanism and dynamic process of explosive spraying. The morphologic and crystallographic results were characterized by SEM and XRD. The magnetic properties were measured via VSM equipment, and the parameters of saturation magnetization Ms, residual magnetization Mr, and coercivity Hc were emphasized in the hysteresis loop pattern. The experimental results indicate that a dense coating was prepared with extremely low porosity, and the morphology of the coating surface shows different regions characterized by solidified chunks and loose particles. XRD patterns showed that crystalline structures were discrepant under two load systems with different Ni weight proportions. Magnetic measurements gave a thin and narrow hysteresis loop, which represents loops with good soft magnetic properties. Quantitatively, coercivity Hc decreased from 59.3 to 52.6 and from 121.0 to 49.9 for the coatings not containing and containing Co under parallel and perpendicular fields, respectively.

(Fe-Ni)-based glassy alloy containing Nb and Cu with excellent soft magnetic properties

Magnetic properties of amorphous Fe38Ni38B12P5Si3Nb3Cu1 alloy ribbons have been investigated in as-spun and annealed states with the aim of developing an ultrasoft magnetic material which is expected to be used in advanced information data devices. A small amount of simultaneous addition of Cu and Nb to a FeNi-metalloid amorphous alloy system caused the change in crystallization process from eutectic type to the primary one. After annealing at the temperature just below the glass transition temperature (Tg), the glassy alloy ribbon exhibit excellent soft magnetic properties, very low coercive force of 1 A/m and extremely high effective permeability of 7.5·104 at 1 kHz which have not been obtained for any kinds of Fe- and Ni-based amorphous alloys, in spite of relatively low saturation magnetic flux density of 0.86 T. The further increase in annealing temperature causes the precipitation of nanoscale fcc particles with a size of about 7 nm including a high density of planar faults and the resulting nanostructure alloy also exhibits good soft magnetic properties with low Hc below 2 A/m. The formation of nanostructure fcc-(Fe,Ni) + glass soft magnetic alloys is also novel. The syntheses of the new Fe-Ni-based glassy and nanocrystalline [fcc(Fe,Ni) + glass] alloy ribbons with ultrasoft magnetic properties are encouraging as a new type of energy saving-type soft magnetic material.

Unveiling heterogeneous microstructure and good combinations of high yield strength and low coercivity of in-situ formed NbC/FeNiCo medium-entropy composites

It is very challenging to achieve exceptional combinations of soft-magnetic and mechanical properties in conventional soft-magnetic alloys. To tailor combinations of soft-magnetic and mechanical properties, different volume fractions of in-situ formed NbC were designedly introduced into the recently emerged equi-atomic FeNiCo medium-entropy alloy displaying appealing soft-magnetic properties but disappointing strength. The bulk NbC/FeNiCo medium-entropy composite (MEC) with ∼7.8 vol% NbC (MEC7.5) consisted of ultra-fine and fine FCC grains with nano-sized NbC, realized the best combinations of mechanical and soft-magnetic properties. In detail, it showed an ultra-high tensile yield strength of ∼1158 MPa and an improved elongation of ∼4.6%, resulting from dislocation strengthening, dispersion strengthening and hetero-deformation induced strengthening. Simultaneously, the saturation magnetization and coercivity of the MEC7.5 were ∼ 143 emu/g and ∼ 382 A/m, suggesting that it has good soft-magnetic properties. Therefore, our findings provide a new paradigm for realizing outstanding combinations of high yield strength and low coercivity in alloys.

Magnetoelectric memory cell based on 0.5Ba(Zr0.2Ti0.8)O3-0.5Ba0.7Ca0·3TiO3/Fe65Co35 thin films

In this study, 0.5Ba(Zr0·2Ti0.8)O3-0.5Ba0·7Ca0·3TiO3(0.5BZT-0.5BCT) thin films were deposited on Pt/Ti/SiO2/Si substrate, and then small area Fe65Co35(FeCo) films were deposited on 0.5BZT-0.5BCT films. The hysteresis loops and piezoelectric curves of 0.5BZT-0.5BCT films were studied. The results show that the piezoelectric displacement of 0.5BZT-0.5BCT films is 63 Å, the residual polarization intensity is 2.76 μC/cm2 and the coercive field is 110 kV/cm. 0.5BZT-0.5BCT/FeCo composite films exhibit typical magnetic hysteresis loops and stripe-like domains, the in-plane and out-of-plane coercivities are 10 Oe and 94 Oe, respectively, which indicates that the thin films have good soft magnetic properties. The current-voltage (I–V) curves of FeCo films on 0.5BZT-0.5BCT films were studied, the I–V behaviors of the thin films could be modulated by applying bias voltage, resulting in a resistance switching behavior. The maximum resistance change is 94% at 10 V bias voltage and 1 V scan voltage.