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FexCo100−x nanoparticles with different stoichiometry ($x = 0$ –100) have been prepared by a facile synthesis process and compositions confirmed using X-ray fluorescence spectroscopy. X-ray diffraction measurements suggest alloy formation in the body-centered cubic (BCC) phase, with a progressive shift of peak positions to account for the stoichiometric changes. The evolution of nanoparticle morphology is from cubic for iron to hexagonal for cobalt, and the entire composition range has been examined. Magnetic behavior has been accessed by Mössbauer spectroscopy and vibrating sample magnetometric measurements, which suggests an increase of magnetization values of iron upon alloying with cobalt. A detailed account of the synthesis scheme has been presented, to achieve uniform alloy nanoparticles in the pristine state with minimum aggregation and surface oxidation, by carefully adjusting the reaction timescales. [ABSTRACT FROM AUTHOR]

This work focuses on making and studying steel conductors with inhomogeneous surface conductivity. Employing such materials (structures) for engineering the high-field pulsed magnets can provide them with enhanced durability. In this work, monotonically changing resistivity was realized by pack chromizing the medium-carbon steels, 30KhGSA and 40Kh, which were treated at 1000 °C in argon for 150 h under the Cr-load of 20 mg/cm2 to obtain a diffuse layer with minimal carbides at the surface. An approach to investigate the resistivity distribution across a diffuse layer after steel chromizing is suggested and involves a stepwise surface grinding, resistance measurement, and analytical processing of experimental data. The resistivity profile obtained by this method is well described by the complementary error function. At the near-surface layer, 30KhGSA and 40Kh steels have almost the same values of resistivity, about 110– $115 ~\mu $ Ohm $\cdot $ cm, which is 2.9–4.3 times higher than that in the bulk depending on steel. A strong correlation, almost a linear dependence, of resistivity with the depth-derived chromium concentration in the material was found. The proposed method allows one to measure the depth-varied resistivity for ferrous alloys with proper accuracy, while it does not require complex measuring equipment compared with other ones. [ABSTRACT FROM AUTHOR]

A variable magnetic permeability is introduced to the skin effect coefficient to reflect the influence of flux density variation on eddy current losses. The evaluation results show that the new iron loss model can cover a wide range of frequencies without using piecewise functions. Two types of punched edges are defined and the additional iron losses are tested, separated, and modeled, so that the punching and burrs’ connection effects on iron losses can be considered more accurately. The iron loss model proposed in this article is very useful for a more accurate design of high-speed motors including the punching effects. [ABSTRACT FROM AUTHOR]

Power losses in soft magnetic materials can be solidly assessed by the statistical theory of losses (STLs), which provides physical foundation to the concept of loss separation. The theory is, however, limited to the conventional case of symmetric hysteresis loops and cannot be straightforwardly applied for a magnetic core operating under a dc bias. We show, in this paper, that such constraint can be released by combining the STL with a simplified approach to the dynamic Preisach model. This approach leads to the more affordable static Preisach model with largely reduced computation time. In this way, the hysteresis and excess loss components, with and without dc bias, are identified and calculated starting from a minimum set of experimental data. We provide a wide-ranging experimental validation of the theory, which is applied to the behavior of the energy loss versus frequency, measured up to $f = 1$ kHz, in non-oriented and grain-oriented iron-silicon sheets and in iron-cobalt alloys, subject to different polarization bias levels. [ABSTRACT FROM AUTHOR]

The tactile perception of an object’s surface material plays an important role in many intelligent fields including object recognition, robotic grasp, and environment exploration. Enlightened by the human active tactile perception process that originates from scanning a finger on the surface, a novel finger-like tactile sensor for surface material recognition has been designed according to the transduction mechanism of cilia and Villari effect of the iron–gallium alloy. Based on the structural dynamic theory of Euler–Bernoulli beam, the linear constitutive equations of magetostrictive material and the Faraday law of electromagnetic induction, the output voltage model of the sensor under vibration induced from the fingertip-surface scanning has been established. Furthermore, a prototype of the sensor, on the macroscale, is fabricated. In order to verify the performance, the sensor is used to measure induced vibration signals with texture properties during sliding on the surface and classify five similar texture surfaces with small differences with a classification algorithm. The experimental results indicate that the proposed tactile sensor is effective and highly accurate for surface material classification. The sensor is characterized by high sensitivity and quick response. It has the potential of being miniaturized and integrated into the finger of a robotic hand to realize surface material recognition in real time. [ABSTRACT FROM AUTHOR]

Two types of surface-mounted permanent magnet synchronous machines (PMSMs) with the same physical dimensions but different stator core materials are comparatively analyzed, prototyped, and tested in this paper. In order to quantify the magnetization and loss characteristics of the stacked amorphous metal (AM) stator core, an experiment is conducted under different supply frequencies. Based on the data, the no-load iron losses, harmonic losses generated by the inverter-induced non-sinusoidal current harmonics, and the $d$ -axis and $q$ -axis inductances of two types of motors are comparatively analyzed by the finite-element method under different conditions and verified by experiments carried out on the two types of PMSM prototypes. The results illustrate that the AM PMSM has a characteristic of extremely low no-load iron losses, relative to the conventional silicon steel PMSM. [ABSTRACT FROM AUTHOR]

This paper investigates the no-load iron loss, on-load loss, and thermal performance of a high-speed surface-mounted permanent-magnet synchronous machine with an amorphous metal stator core (AMSC) and a titanium alloy retaining sleeve by numerical methods. The electromagnetic properties of the AMSC are tested by an experimental platform. The distributions of no-load iron loss, rated-load loss, and the thermal behavior of the motor are investigated under converter supply conditions. Finally, the loss and thermal performances of the prototype are tested and compared with the corresponding simulation results to verify the accuracy of the calculation results and the superiority of the prototype. [ABSTRACT FROM AUTHOR]

One of the issues of an iron loss estimation is the modeling of an excess loss. This paper investigates the modeling method for the excess loss under dc-biased conditions. The proposed approach is based on the 1-D finite-element analysis for the silicon steel sheet in the thickness direction considering hysteretic property and skin effect. In addition, the magnetic flux density waveform is divided into the outline loop and minor loops and estimate the excess loss of each loop using the eddy current loss correction factor $\kappa $ taking account of dc-biased conditions. To demonstrate the effectiveness of the proposed method, we compare the estimated loss with measured one for the harmonic wave in single sheet tester. [ABSTRACT FROM AUTHOR]

To evaluate the iron losses of motors and three-phase transformers, the rotational iron loss should be considered. A simple numerical calculation method of the rotational iron losses under rotational flux with high flux density and different axis ratios is proposed in this paper. First, it is shown that the method of decomposing the rotational flux into the directions of the major and minor axes of the rotational flux is effective in calculating the rotational iron losses of the non-oriented and grain-oriented electrical steel sheets in low magnetization region. Then, the simple iron loss calculation method is improved to consider the decrease of rotational hysteresis and anomalous eddy current losses in high magnetization region under circular rotational flux and verified by comparing with measurement results. Furthermore, it is improved to be applicable to rotational iron loss calculation under rotational flux with different axis ratios and verified by comparing with measurement results. [ABSTRACT FROM AUTHOR]

The effect of an initial alloy on microstructure and magnetic properties of Nd–Fe–B hydrogenation–disproportionation–desorption–recombination (HDDR) magnets during hot-deformation process have been studied with strip-casting alloy of composition Nd12.5FebalCo0.3Nb0.2B6.4 which have different microstructures. HDDR powders were produced by HDDR process with strip-casting alloy after pre-annealing or no pre-annealing. Obtained HDDR powders were subjected to hot-pressing at 700 °C under 400 MPa in vacuum and subsequently to die-upsetting at 800 °C with deformation conditions such as strain rate of 0.01 s−1 and height reduction of 77%. The microstructure of the initial alloys showed a large difference depending on the presence or absence of pre-annealing. The coercivity of HDDR powders using alloy after pre-annealing and no pre-annealing was different about 2 kOe. In addition, the remanence of hot-deformed magnet using HDDR powder produced with no pre-annealing alloy was higher than that with pre-annealing alloy although the hot deformation was conducted under the same condition and the remanence of two kinds of starting HDDR powder was almost the same. It was confirmed that the microstructure and magnetic properties of hot-deformed magnet depend on the microstructure of the initial alloy. [ABSTRACT FROM AUTHOR]

The phase transformation of FeV ($\sigma$ -phase) to Fe2VAl (L21-phase) has been studied by systematic variation of Al concentration in Fe2V2−xAlx ($x = 0-1$). Remarkable changes in magnetic properties were observed with different Al contents. Electrical transport and magnetic properties of these compositions have been investigated in the temperature range, which revealed that the disorder and impurity phase plays an important role in tuning the electronic properties. The observed magnetic anomalies above $\mathrm{T}_{C}$ indicate the heterogeneous magnetic nature of these alloys. The role of Al in electronic transport and the correlation between structural, magnetic, and electrical transport properties are discussed. [ABSTRACT FROM AUTHOR]

We report on fabrication and magnetic properties of high Bs-Fe76Si9B10P5 and Fe81.5Si0.5B4.5P11.0Cu0.5C2.0 alloy powders by gas atomization. Different atomizing gases such as Ar, N2, and He were used to understand their effects on cooling rate and powder particle size. We show that the amorphous powders of Fe76Si9B10P5 alloy with spherical shape and sizes below 90 $\mu \text{m}$ can be obtained easily with Ar gas. This situation strongly changes for the alloy with higher concentration of Fe, i.e., Fe81.5Si0.5B4.5P11.0Cu0.5C2.0. Only powder particles with sizes below 10 $\mu \text{m}$ were amorphous, when Ar was used as an atomizing gas. He and N2 gases allow higher cooling rates, and powders with sizes below 20 $\mu \text{m}$ become almost amorphous. In addition, an improvement in the yield of smaller sized powders is noticeable. We made toroidal cores of powders with different sizes by mixing with a polymer resin, and pressing under a pressure of 1.5 GPa. The powder cores were annealed at different temperatures. Effect of structure (amorphous and nanocrystalline), and powder particle sizes on core loss, and initial relative permeability were investigated. Lower core loss with a constant initial relative permeability up to more than 100 MHz can be obtained for the cores made from powders of sizes below 10 $\mu \text{m}$. The magnetic cores reported in this paper are promising for high-power and high-frequency applications. [ABSTRACT FROM AUTHOR]

The effects of the partial substitution of Mn by Co/Fe on the structural, magnetostatic, and magnetodynamic properties of Ni–Mn–In Heusler alloy films were studied using X-ray diffraction, field-dependent magnetization, and ferromagnetic resonance studies. It was observed that the substitution of up to 3 at.% Co or Fe atoms in Mn sites does not alter the crystal structure much. However, an increase in grain size and surface roughness was noticed upon substitution of the fourth element. The magnetic moment of the films could be increased up to 120 kA/m by introducing Co/Fe in Mn sites. For the first time, low Gilbert damping constant ($\alpha$) of 0.008 is observed in Co substituted Ni–Mn–In film together with high saturation magnetization, high perpendicular anisotropy, and an easy axis along film plane, which are the promising factors for application in high-density random-access memory devices. [ABSTRACT FROM AUTHOR]

Two types of re-substituted (FeCo)2B-type alloys with stoichiometric (Fe0.675Co0.3Re0.025)2B and 1.5 at% boron-excess compositions were prepared by suction casting and subsequent mechanical milling and annealing. Phase evolution in the (FeCo)2B-type alloys in the course of mechanical milling and annealing was investigated. Single-phase re-substituted (FeCo)2B-type material was prepared from stoichiometric (Fe0.675Co0.3Re0.025)2B by the combination of suction casting and mechanical milling. The two alloys had the same phase constitution of (Fe, Co)2B-type and amorphous phases in heavily milled state. However, the heavily milled alloys had different phase constitution after annealing; the stoichiometric alloy consisted of single (Fe, Co)2B-type phase, while the boron-excess alloy consisted of two-phase mixture of (Fe, Co)2B-type and (Fe, Co)B-type phases. The two heavily milled alloys had similar coercivity of around 1 kOe after full annealing. [ABSTRACT FROM AUTHOR]

We report on the magnetic properties of NdFeB powders produced by gas atomization, which is a powder manufacturing technology scarcely used in the past to produce such alloys. Using this technique, we have produced several ternary NdFeB alloys with Nd contents between 26.9 wt.% and 28.5 wt.%. The as-atomized powders were split into different size fractions by sieving. Subsequently, we measured the magnetic properties as a function of temperature, between 10 and 400 K, and particle size. The magnetic behavior depends strongly on the microstructure of the material, which in turn is determined by the particle size. It is reported a slope anomaly in the curve of magnetization as a function of temperature at around 150 K due to a spin-reorientation transition. Since gas-atomized powders are isotropic, this magnetic transition produces an increment of the magnetization below this temperature. [ABSTRACT FROM AUTHOR]

In this paper, we report the effect of thermal treatment at different temperatures (523, 623, and 723 K) on the magnetic properties of an amorphous powder with composition Fe72.5Si12.5B15 obtained by gas atomization. Differential scanning calorimetry curves indicate that a significant structural rearrangement takes place during annealing before crystallization. As expected, the intrinsic coercivity decreases with the annealing temperature, being the most significant drop from 3.26 to 0.44 Oe for the powder with a particle size $< 20~\mu \text{m}$ , non-annealed, and annealed at 723 K, respectively. An analysis of the effect of annealing on the anisotropy field distribution obtained directly from the magnetization curve is presented for both the non-annealed and the annealed sample with the lowest value of coercive field. The probability density function of the anisotropy field exhibits a lower applied field value at the maximum and is better fit by a Gaussian distribution after the heat treatment, which is a sign of better amorphicity after structural relaxation. [ABSTRACT FROM AUTHOR]

The authors proposed the iron-based metal composite bulk magnetic core for high efficient and lightweight MHz switching DC–DC converter using SiC/GaN power devices. Although the iron-based metal composite bulk magnetic core exhibited a lower core loss than that of Ni-Zn ferrite in MHz frequency band, its relative permeability was low around 10. In this paper, in order to increase the permeability of such composite magnetic core with low core loss, we investigated an effect of mixing amorphous alloy powder having different particle size distributions. This method estimated increasing volume fraction of amorphous alloy powder and decreasing the demagnetization field of the composite magnetic core. From the experimental results, the composite magnetic core with an optimal mixing ratio of 2.4 $\mu \text{m}$ and 12.8 $\mu \text{m}$ median diameter Fe-based amorphous alloy (Fe-AMO) powders exhibited a relative permeability of 20.5 which was 2.4 times higher than that of composite magnetic core using 2.4 $\mu \text{m}$ median diameter Fe-AMO powders. And its core loss was 555 kW/m3 at 1 MHz in frequency and under 20 mT in maximum flux density. [ABSTRACT FROM AUTHOR]

Thermal properties of submicrometer wires of Pd-doped FeRh alloys are evaluated from measurements of transport properties around the first-order antiferromagnetic to ferromagnetic phase transition. Recently, in a submicrometer wire of FeRh alloy, an asymmetric structure between heating and cooling processes was reported in the vicinity of the phase transition temperature. A system where finite-size effects appear is expected to show different magnetic and thermal properties from those in bulk and thin film. However, thermal or magnetization measurements are difficult to perform on samples with such a tiny volume. Here, we demonstrate a quantitative evaluation of thermal properties in thin films and submicrometer wires of B2-ordered Pd-doped FeRh alloy grown on MgO (001). Resistivity measurements on a series of wires with different widths reveal that the anomaly in the resistance change is enhanced in narrow wires. As the transport properties in submicrometer wires sensitively reflect those magnetic states, the entropy change and the irreversible energy loss during the first-order phase transition have been determined via resistance measurements. We find a larger energy loss in smaller samples where wider hysteresis loops appear in temperature-driven measurements. This method can be a probe to evaluate the finite-size effect induced by a restricted magnetic domain nucleation process during the phase transition. [ABSTRACT FROM AUTHOR]

Nd-Fe-B magnetic powders produced by the hydrogenation-decomposition-desorption-recombination process have a lower squareness ratio than sintered magnets. In this paper, the anisotropy field ($H_{k}$) distribution was assumed to be a horizontally flipped lognormal distribution and the effect of the $H_{k}$ dispersion on the squareness ratio was investigated by using a micromagnetic simulator. As a result, the squareness ratio was very similar to the experimental demagnetization loop, when $\langle H_{k}\rangle $ was 5500 kA/m and $\sigma H_{k}/\langle H_{k}\rangle $ was 30%. Moreover, we investigated the easy axis dispersion of grains on squareness ratio in consideration of soft magnetic or nonmagnetic grain boundaries. As a result, the squareness ratio for the nonmagnetic grain boundary was closer to the experimental value; however, it is difficult to describe the experimental demagnetization loop by only considering the easy axis dispersion. [ABSTRACT FROM AUTHOR]

The Curie temperature distribution induced from grain size variation in heat-assisted magnetic recording (HAMR) can be alleviated by including the thermally insulating magnetic grain boundaries. In this paper, we present a systematic micromagnetic study on this new type of HAMR media, focusing on the impact to the recording behaviors from the exchange coupled magnetic boundary (shell). It is found that the soft magnetic shell of higher Curie temperature is capable of assisting the switching of FePt grain in both magnetization and transition process. The important implication of the proposed media for practical HAMR recording is that optimal performance now can be accomplished with relaxed recording conditions in both head field intensity and the heating source, eventually enhancing area density capability and the overall HAMR system stability. [ABSTRACT FROM AUTHOR]

Fe-based amorphous thin films of two compositions (Fe80B20 and Fe65.6Co9.4B25) were deposited by RF magnetron sputtering with and without applying an in situ magnetic field along the films’ in-plane direction. In addition, films with varying thickness were deposited for each composition. Hysteresis loops and residual stress were measured and compared to study the effect of in situ fields on the magnetic and magnetostrictive behavior of the films. Results showed that in situ magnetic fields can lower the in-plane coercivity for the Fe80B20 films. Also, when the residual stress was below a certain level, its distribution in different directions shows a uniaxial feature due to the applied in situ field. This uniaxial distribution of stress adds an extra magnetoelastic anisotropy to the films. This paper provides insight for optimizing magnetic thin films’ properties for applications where the magnetostriction is relevant, in terms of the in situ magnetic field, coercivity, and residual stress. [ABSTRACT FROM PUBLISHER]

Magnetic components prepared using Fe–Si–Cr alloy powders have been widely used in high-current power inductors due to their high initial permeability, high-saturation magnetization, and excellent dc-bias characteristics. Fe–Si–Cr alloy bodies were prepared in this paper using a uniaxial molding press at different compaction pressures. Samples were then annealed at different temperatures to form a chromium-rich oxide insulating layer on the powder surface to reduce the core loss. The compaction pressure and the annealing temperature effects on the microstructure, internal strain, and insulating layer thickness and the electromagnetic properties for Fe–Si–Cr alloy powder compacts were investigated. The results showed that the relative density gradually increased with increasing compaction pressure, leading to increased saturation magnetization, thereby improving the initial permeability from 29 to 37. After annealing, the internal strain was reduced, which resulted in the initial permeability increasing substantially. Moreover, the electric resistivity and dc-superposition characteristics also increased with increasing heat treatment temperature. However, excessively thick insulating layer formed on the Fe–Si–Cr alloy powder surface resulting from annealing at too high temperature leading to initial permeability and saturation magnetization degradation. [ABSTRACT FROM PUBLISHER]

In many electromagnetic energy conversion processes, transformers, or electric machines are controlled with modern power converters at high frequencies up to a range of several 10 kHz. Such operation modes lead to not negligible, distinct iron losses in the flux-leading laminated core. For estimating iron losses, no universally valid equation is available covering transient effects and nonlinear magnetization processes at the same time for a wide frequency range. Sophisticated 2-D and 3-D models are available but these hysteretic models are computationally very intensive when applied in a finite-elements method. This paper presents a 1-D iron-loss model, which allows estimating the static and dynamic hysteresis losses during the electromagnetic energy conversion processes with low computational effort. The proposed model can be used as lumped circuit element in a spatial magnetic equivalent network representing an electromagnetic device e.g., an induction machine. The model is based on a loss-separation approach, in which the different magnetization-loss mechanisms are interpreted corresponding to an analogous mechanical model. The proposed approach is implemented in Modelica; the model setup and the simulations are performed in Dymola. The validation of the developed iron-loss model is performed with measurements conducted on an Epstein frame. [ABSTRACT FROM AUTHOR]

FeCuPt nanodot arrays were fabricated by electrodeposition onto a nanopore patterned substrate fabricated by electron beam lithography (EBL), for the purpose to manufacture and characterize model bit-patterned media. Addition of Cu to FePt was carried out to accelerate the phase transformation of FePt into the L10 -ordered phase in order to fabricate nanodot arrays with hard and uniform magnetic properties. Composition of the FeCuPt ternary alloy films was optimized by varying applied potential and CuSO4 concentration to form single L10 phase (40–50 at% Pt and ~25 at% Cu). Annealing at 450 °C resulted in the phase transformation from fcc to L10 in FeCuPt ternary alloy films, whereas FePt binary alloy films did not show a phase transformation. Perpendicular coercivities of FeCuPt and FePt were 6 and 1 kOe, respectively, annealing at 450 °C, indicating the formation of the L10 phase with lower annealing temperature by Cu incorporation. FeCuPt nanodot arrays with 20 nm in diameter and 35 nm in pitch were successfully fabricated with the nanopore patterned substrate fabricated by EBL. In addition, cross-sectional transmission electron microscope analysis of FeCuPt nanodot arrays showed clear stacking of the L10 (111) lattice in a perpendicular direction through the growth direction having a single crystal nature, whereas phase transformation was insufficient with FePt nanodot arrays. The collective results have successfully demonstrated the electrochemical fabrication of ultra-fine FePt nanodot arrays with L10 structure by promoting L10 ordering with Cu additions. [ABSTRACT FROM PUBLISHER]

We investigate the Gilbert damping and the magnetization switching of perpendicularly magnetized FeCoB-based free layers (FLs) embedded in magnetic tunnel junctions adequate for spin-torque-operated magnetic memories. We first study the influence of the boron content in MgO/FeCoB/Ta systems alloys on their Gilbert damping parameter after crystallization annealing. Increasing the boron content from 20% to 30% increases the crystallization temperature, thereby postponing the onset of elemental diffusion within the FL. This reduction of the interdiffusion of the Ta atoms helps maintaining the Gilbert damping at a low level of 0.009 without any penalty on the anisotropy and the magnetotransport properties up to the 400 °C annealing required in CMOS back-end-of-line processing. In addition, we show that dual MgO FLs of composition MgO/FeCoB/Ta/FeCoB/MgO have a substantially lower damping than their MgO/FeCoB/Ta counterparts, reaching damping parameters as low as 0.0039 for a 3 Å thick tantalum spacer. This confirms that the dominant channel of damping is the presence of Ta impurities within the FeCoB alloy. On optimized tunnel junctions, we then study the duration of the switching events induced by spin-transfer torque. We focus on the sub-threshold thermally activated switching in optimal applied field conditions. From the electrical signatures of the switching, we infer that once the nucleation has occurred, the reversal proceeds by a domain wall (DW) sweeping though the device at a few 10 m/s. The smaller the device, the faster its switching. We present an analytical model to account for our findings. The DW velocity is predicted to scale linearly with the current for devices much larger than the wall width. The wall velocity depends on the Bloch DW width, such that the devices with the lowest exchange stiffness will be the ones that host the DWs with the slowest mobilities. [ABSTRACT FROM PUBLISHER]

Fe–Ga (Galfenol) is a rare-earth-free alloy with useful magnetostrictive properties of nominal cost and robust mechanical properties advantageous for sensing, actuating, and energy harvesting. Understanding magnetostriction and magnetization behaviors under stress while at temperatures up to +250 °C is needed to explore the potential of harsh environment applications for magnetostrictive non-contact sensors, for use in applications such as monitoring torque changes in engines and rotorcraft shafts. Galfenol thin patches have the potential to operate in these applications, but alloy performance at these temperatures while under stress has not been studied. Thus, in this paper, we investigate simultaneous effects of temperature and compressive stresses on magnetic and magnetostrictive behaviors of single crystal Fe–Ga samples at temperatures from +25 °C to +250 °C while under compressive stresses of 0, 15, and 23 MPa. The samples are also subjected to temperatures up to +250 °C and no stress to acquire simultaneous magnetostriction and magnetization values. Building upon this experimental data, this paper attempts to relate temperature dependence and shape anisotropy to determine the effect on magnetic susceptibility at elevated temperatures. Understanding the roles of temperature and compressive stress as well as shape anisotropy on magnetostrictive, Fe–Ga alloys can provide an advanced understanding of the material properties and thus facilitate their use in a wider range of applications. [ABSTRACT FROM AUTHOR]

Two FeAlB polycrystalline alloys were stress annealed and had the piezomagnetic behavior determined before and after the stress annealing (SA). The concentration of boron is constant, 1.6% (at%). The alloys are basically formed by the phase Fe2B dispersed in a bcc matrix. The bcc matrix can be formed of a disordered and/or ordered structure, depending on ratio of Fe:Al, that was fixed as 86Fe:14Al and 80Fe:20Al. Magnetostriction and magnetic induction were measured as a function of magnetic field and compressive stresses. The piezomagnetic coefficient d33\equiv ~\text{d}\lambda /\text{d}H improvement due to SA was achieved, in which $\lambda$ is the magnetostriction and H the applied magnetic field. SA causes the reorientation of the magnetic moment of the material creating an artificial magnetic anisotropy. The behavior of the coefficient d33 varies due to changes in Al content, since the magnetocrystalline anisotropy of the alloy depends on the ordering of the bcc matrix. Values of d33 up to 4 nm/A were reached for the polycrystalline alloy with 14% Al (at%) in an interval of compressive stresses of $0 \le \vert \sigma \vert \le177$ MPa. This large interval of compression stress is due to the presence of the Fe2B phase. [ABSTRACT FROM AUTHOR]

Amorphous magnetic CoFeB ultrathin films have been synthesized on the narrow band gap semiconductor InAs(100) surface, and the nature of the interface magnetic anisotropy and electrical contact has been studied. Angle-dependent hysteresis loops reveal that the films have an in-plane uniaxial magnetic anisotropy (UMA) with the easy axis along the InAs [0-11] crystal direction. The UMA was found to be dependent on the annealing temperatures of the substrates, which indicates the significant role of the Fe, Co-As bonding at the interface related to the surface condition of the InAs(100). $I$ – $V$ measurements show an ohmic contact interface between the CoFeB films and the InAs substrates, which is not affected by the surface condition of the InAs (100). [ABSTRACT FROM PUBLISHER]

One-dimensional magnetic materials find several applications in modern technology. Co–Fe alloys and their oxides CoxFe2–xO3 ( $0 \leq \times \leq 0.7$ ) were prepared using a very simple and novel technique. The X-ray diffraction patterns confirm the coexistence $\alpha $ -Fe2O3 and $\varepsilon $ -Fe2O3 phases in the as-prepared as well as the sample sintered in N2 atmosphere. In contrast, samples sintered in H2 atmosphere could provide Co–Fe alloys and $\alpha $ -Fe2O3 composites. Nanorod shapes for oxide samples were corroborated by scanning and transmission electron microscopy. A reasonably high coercivity value ( $\sim 118$ mT) was observed for such rods, whereas a sufficiently high saturation magnetization value near 162 Am2/kg was obtained for other types of composites. [ABSTRACT FROM AUTHOR]

The small-signal vibration model of TbxDy1–xFey plate was developed by mechanical-electrical analogy method. Based on the model, we demonstrated the reasonableness of measuring the small-signal magnetomechanical behaviors by a laser Doppler vibrometer. The strain coefficient of the TbxDy1–xFey plates was measured as a function of frequency and bias field ( H\mathrm{ dc}) , and Young’s modulus, mechanical quality factor ( Qm) , relative permeability, and magnetomechanical coupling coefficient were investigated as a function of H\mathrm{ dc} . Many novel characteristics were observed under the drive of a small-signal field (7.96 A/m). The change tendency of the strain coefficient at resonance differs from that at low frequency, and the resonant strain coefficients are significantly high (>85 nm/A) in a wide range of bias field from 4.78 to 55.72 kA/m. Both the negative- \Delta E and positive- \Delta E effects are observed, and the negative- \Delta E effect in the low field range is also remarkable. In particular, sharply decreases from the initial value of 104 to a minimum value of 11.4 and, then, increases slowly, and the ratio of the maximum variation of Q_{m} over H\mathrm{ dc} to the minimum value of Q_{m}$ exceeds $\sim 812.3$ %. This is an important systematic investigation on the small-signal dynamic magnetomechanical behavior of TbxDy1–xFey, and the results are highly beneficial to the designing of magnetostrictive devices. [ABSTRACT FROM PUBLISHER]

Magnetic compaction is a well-known and effective method to improve the coercivity of Nd–Fe–B sintered magnets. During magnetic compaction, the application of an external magnetic field causes the anisotropic alignment of Nd2Fe14B grains as a ferromagnetic phase. After the magnetic compaction, the sintering process is carried out to densify the Nd–Fe–B compacts. In this paper, to identify the relationship between the anisotropic alignment of Nd2Fe14B grains and the densification behavior during the sintering process, we phenomenologically analyzed the shrinkage of magnetically compacted Nd–Fe–B sintered magnets according to the directions of magnetic field that were perpendicular direction and parallel direction to the magnetic aligned direction. In addition, the shrinkage and the grain size were measured at various sintering temperatures. It was concluded that the difference in the shrinkage and grain growth rates between the directions that are the perpendicular and the parallel could be evaluated based on their anisotropic characteristics and the crystal structure of the Nd2Fe14B phase. Shrinkage analysis indicated that the perpendicular direction to the magnetic aligned direction yields a larger shrinkage compared with the parallel direction to the magnetic aligned direction. In addition, grain size analysis revealed that the grain size was $\sim 10$ % larger in the perpendicular plane as compared with the grain size in the parallel plane. [ABSTRACT FROM PUBLISHER]

In this paper, a method to improve the magnetic and structural properties of heat-assisted magnetic recording media by applying partial substrate bias during the deposition of FePt-based recording layer is demonstrated. Although the application of a substrate bias for the entire FePt layer deposition deteriorated the media properties, improvements were noted when a substrate bias is selectively applied for the deposition of top portion of the FePt layer. Our experiments suggest that the compressive stress due to the ion peening in the biased deposition degrades the texture and magnetic properties of the FePt media, primarily during the initial phase of FePt film growth. On the other hand, the media fabricated by applying an optimum substrate bias for the deposition of top portion of the FePt layer showed improvements in the micro-structural and magnetic properties. [ABSTRACT FROM PUBLISHER]

This paper presents the preliminary evaluation results of a magnetorheological elastomer (MRE) patch fabricated by oriented flake-type Fe–Ga alloy (Galfenol) particles bound in a silicone polymer matrix. A force/pressure sensor, based on the Galfenol MRE patch, was developed to verify the advantages of the MRE with magnetically aligned Galfenol flakes. Hall effect sensors embedded in the MRE sensing device detect the change of magnetic flux density due to the deformation of the Galfenol MRE patch induced by an externally applied force with non-magnetic disturbance. The Galfenol flakes are standing up and well aligned to the out-of-plane of the MRE patch using a 1 in diameter permanent magnet, parallel to the applied force direction to improve sensing performance and sensitivity. It was measured at $\sim 105$ mV in the sensor response to a thumb pressure, which exhibited five times higher sensing performance compared to that of another MRE patch with the Galfenol flakes aligned to the in-plane direction. [ABSTRACT FROM PUBLISHER]

We have already reported a prediction method of flux losses (FLs) in bonded magnets and showed good agreement between the calculated losses and the measured ones. In this paper, we improve our previously reported method, and investigate a FL of a Nd–Fe–B-bonded magnet under external magnetic fields. To verify the validity of the prediction method for the FL, we evaluated and calculated a FL of a cylindrical Nd–Fe–B-bonded magnet under the external magnetic fields of −240, −480, and −720 kA/m. The FL of the magnet exposed at 120 °C depended on the strength of the external field, and the measured values of the loss were 8.79% for −240 kA/m, 61.2% for −480 kA/m, and 149.9% for −720 kA/m. The calculated values were 6.44%, 61.1%, and 141%, and we obtained good agreement between the measured and calculated ones. From the results, we conclude that our improved method is effective to predict the FL of the Nd–Fe–B-bonded magnets under external magnetic fields. [ABSTRACT FROM PUBLISHER]

We investigated the influence of thermal deformation on the magnetic properties of flexible FeGa/IrMn exchange-biased (EB) bilayers grown on polyvinylidene fluoride (PVDF) membranes with the pinning direction parallel to the thermal deformation directions \alpha 31 and \alpha 32 of PVDF. Because with increasing temperature, the uniaxial anisotropy is reoriented from the \alpha 32 to \alpha 31 directions by the thermally induced compressive strain along the \alpha 32 direction, both the coercive field Hc and the loop squareness Mr/Ms of FeGa/IrMn bilayers display a complex temperature-dependent behavior. The EB field Hc decreases with increasing temperature. A modified Stoner–Wohlfarth model was employed to account for the temperature dependence of magnetic properties in the flexible FeGa/IrMn bilayers. [ABSTRACT FROM PUBLISHER]

This paper analyzes the output characteristics of a Galfenol magnetostrictive displacement sensor based on the Wiedemann effect, the Jiles-Atherton model, and the piezomagnetic effect. The sensor which is subjected to simultaneously circumferential excitation magnetic field, bias magnetic field, and stress will induce an output voltage. Experiments were performed to describe the induced output voltage versus the applied magnetic fields and stress with an Fe83Ga17 alloy wire as a function of the circumferential excitation magnetic field from 0.5 to 6 kA/m, the bias magnetic field of 3.5 kA/m, and the stress from 5 to 110 MPa. The induced output voltage increases with an increasing magnetic field and decreases with increasing stress. The experimental results agree well with the model calculations. The sensor with a Galfenol alloy wire can be used in displacement control and interface measurement. [ABSTRACT FROM PUBLISHER]

Enhancement of magnetic performance of the Nd–Fe–B-type die-upset magnet by using RF3 (R = Dy, Pr, Nd, Ce, La)-doping as a source of rare-earth substituent was investigated. Commercial melt-spun flakes of Nd13.6Fe73.6Co6.6Ga0.6B5.6 were mixed with 1.6 wt.% RF3 (R = Dy, Pr, Nd, Ce, La) powder. The mixture was hot pressed and then die upset. Coercivity of the die-upset magnet was enhanced by RF3 (R = Dy, Pr, Nd)-doping without severely sacrificing magnetic performance. In the RF3-doped magnet, active substitution between the R atoms from the added RF3 and the Nd atoms in the neighboring flakes occurred to form thin R-diffused shells near the surface of the flakes. Coercivity enhancement for the RF3 (R = Dy, Pr)-doped magnet was largely attributed to the enhancement of the anisotropy field of (Nd,Dy)2Fe14 B- or (Nd,Pr)2 Fe14 B-type grains in the R-diffused shell on the flake surface. Coercivity enhancement in the NdF3-doped magnet was attributed to grain boundary restructuring in the R-diffused shell region. [ABSTRACT FROM PUBLISHER]

Equal channel angular pressing (ECAP) is a well-established thermo-mechanical processing technique, which could induce the c -axis texture of Nd2Fe14B in a melt-spun Nd13.5Fe73.8Co6.7B5.6Ga0.4 alloy. However, the effects of ECAP processing parameters, such as temperature, back pressure (BP), and multiple-pass ECAP routes, remain unknown for this alloy. In this paper, we have investigated the effects of these processing parameters on the c -axis texture formation. It is found by X-ray diffraction macrotexture analysis that the maximum intensity of (001) pole figures for the tetragonal-Nd2Fe14B phase ( I\max ) shows an increase from 2.7 to 4.1 m.r.d. (multiples of random distribution) by increasing the ECAP temperature from 723 to 823 K, while the difference in remanent magnetization between easy and hard directions ( \Delta Mr ) rises from 24.0 to 41.5 Am2/kg. When the BP was increased from 0.25 to 0.5 GPa at 823 K, I\max showed an increase from 2.8 to 4.1 m.r.d. However, I\max saturated for BPs above 0.5 GPa, suggesting that BP has limited effect on the texture formation, although it is necessary for the compaction of the alloy powders. Two multiple-pass ECAP routes conventionally known as routes A and C were employed for two-pass ECAP at 823 K. It is found that route A processing is effective in enhancing the texture formation, while the texture is lost by a subsequent pressing when adopting route C. Therefore, the compaction of Nd13.5Fe73.8Co6.7B5.6Ga0.4 alloy powder using route A ECAP passes with 0.5 GPa BP at 823 K results in pronounced texture, which is beneficial for anisotropic hard magnetic properties. [ABSTRACT FROM PUBLISHER]

This paper reports magnetic, magnetostrictive, and piezomagnetic experimental results performed on a pure iron and a Fe–B alloy, and associated modeling. Results allow a better understanding of the role of Fe2B phase in Fe–Al–B alloys. [ABSTRACT FROM AUTHOR]

The room temperature magnetostriction of polycrystalline Fe100–xCrx alloys annealed at 800 °C was investigated as a function of Cr content varying from 10 to 30 at.% Cr. All alloys exhibited a single bcc \alpha -Fe–Cr phase with a disordered A2 structure. With increasing Cr concentration, the grain shape became very elongated. The greatest total magnetostriction value of 70 \times 10^{-6} was obtained in the direction of the elongated grains for 30% of Cr. We also investigated the effect of B addition on the magnetostriction and structural properties of the alloy Fe80Cr20. Although the addition of B was expected to form the Fe2B phase, the B-added Fe–Cr alloy forms a ternary phase (FezCr1–z)2B ( 0 < z < 0.55$ ), a weak magnetic phase. [ABSTRACT FROM AUTHOR]

Hydrogen absorption (HA) capacity of Sm(CobalFexCu0.053Zr0.02)7.84 ( $x=0.2$ , 0.3, 0.4, 0.5) as-cast alloys was improved through increasing Fe content and its mechanism was symmetrically analyzed. X-ray diffraction analysis indicates that the main phase of all as-cast alloys was 1:7 phase. Due to lower electronegativity of Fe than that of Co, activation energy of chemical adsorption for 1:7 phase was reduced with increasing Fe content. Due to larger atomic radius of Fe than that of Co, lattice parameters and lattice gaps of 1:7 phases were enlarged with increasing Fe content, and diffusion barrier of H atoms was lowered resulting from increasing lattice parameters and sizes of lattice gaps. These all strengthened the HA capacity of 1:7 phase. Two principles are mentioned to provide theoretical guidance for strengthening HA capacity by adding other elements. [ABSTRACT FROM AUTHOR]

First principles calculation for the energies and magnetic moments of Fe2CrAl with various structures has been carried out. The contradiction between theoretical and experimental magnetic moment of Fe2CrAl has been illustrated. The L21-based structure has the lowest energy and thus should be formed during synthesis, while the native magnetic Cr-clusters are responsible for the extra large magnetic moment. Based on these calculations, a metastable and partially disordered B2CD structure has been achieved in a ball-milled Fe2CrAl alloy. It shows a 300 K higher TC and a 1.5 \mu {B} higher MS, respectively, compared with the arc-melted samples with L21-based structures. [ABSTRACT FROM AUTHOR]

In this paper, a series of FeCuNbSiB/Terfenol-D/PZT (F/M/P) multiphase laminate heterostructures is presented, whose magnetoelectric (ME) coupling characteristics have been investigated. Compared with the traditional Terfenol-D/PZT (M/P) composites, the ME coupling characteristics of the proposed F/M/P heterostructures were significantly improved. The resonant and low-frequency ME voltage coefficient of the F/M/P heterostructures could be tuned by controlling the layers number N . In addition, the ME field coefficient of F/M/P heterostructures increases sharply and tends asymptotically toward a certain limiting value with the increase of thickness ratio t_{m}/t_{p} . When N$ is 7 (FMPMPMF), the maximum value of resonant ME voltage coefficient achieves 8.69 V/Oe, which is \sim3.65$ times higher than that for FMP, 1.81 times higher than that for FMPMF. Meanwhile, the maximum value of low-frequency ME voltage coefficient for FMPMPMF heterostructures achieves 69.6 mV/Oe at {H_{b}} = 378 Oe. Remarkably, it indicates that the F/M/P heterostructures have great potential as far as its application in highly sensitive dc magnetic field sensing and vibration energy harvesting. [ABSTRACT FROM AUTHOR]

In this paper, large zero-biased magnetoelectric (ME) effects are experimentally demonstrated in a five-phase laminate composite consisting of high-permeability Fe-based soft magnetic alloy FeCoV, giant magnetostrictive material Terfenol-D, and piezoelectric ceramic Pb(Zr1−x, Tix)O3 (PZT). The coupling effects between FeCoV and Terfenol-D result in a build-in magnetic bias due to their different magnetic permeability and coercivity. As a result, an obvious increase in resonant ME voltage coefficient (MEVC) at zero dc magnetic bias field ( H\text {dc}) for FeCoV/Terfenol-D/PZT/Terfenol-D/FeCoV (FMPMF) composite is obtained. The experimental results demonstrate that the optimum zero-biased resonant MEVC ( \alpha \text {ME,r}) of FMPMF composites with three-layer FeCoV foils can reach 19.6 V/cm Oe, which is 1.75 times as great as that of traditional Terfenol-D/PZT/Terfenol-D (MPM) laminate composites. A low-frequency MEVC ( \alpha \text {ME,l}) of 176 mV/cm Oe is achieved, which is 2.45 times higher than that of the MPM laminate composites. The induced zero-biased ME voltage of FMPMF laminate composite shows an excellent linear relationship to ac magnetic field both at the low frequency (1 kHz) and the resonance frequency (115.14 kHz) over a wide range. This laminate composite shows promising applications for high-sensitivity and small-size magnetic-sensing devices without bias. [ABSTRACT FROM AUTHOR]

Anisotropic Nd–Fe–B films with high performance have been prepared by dc magnetron sputtering on heated Si(100) substrates. The influences of sputtering power, target composition, deposition temperature, and annealing condition on the magnetic properties of Nd–Fe–B films were investigated systematically. The X-ray diffraction patterns showed that the Nd–Fe–B grains are aligned with their c-axes pointing normal to the film plane. It was found that the magnetic properties are sensitive to the target composition, deposition temperature, and sputtering power. The maximum energy product achieved (378 kJ/m3) is comparable with that of high-quality Nd–Fe–B sintered magnets. [ABSTRACT FROM AUTHOR]

It is revealed by magnetic field analysis that a difference between an actual reactor loss and a material datasheet loss, which was observed by measurement using an actual reactor with air gaps under high-frequency excitation, is caused by leakage magnetic flux near the air gaps of a reactor. In our previous measurement, an actual reactor loss under high-frequency excitation became large compared with a datasheet loss of the reactor core material. To clarify the reason, we carry out a 3-D magnetic field analysis. As a result, due to the increasing eddy current losses by leakage magnetic flux density near reactor gaps and due to the ununiform distributions of an iron loss caused by leakage magnetic flux, the reactor loss becomes larger than that of the datasheet loss. [ABSTRACT FROM AUTHOR]

Nd–Fe–B-based alloy powders were subjected to the dynamic hydrogen disproportionation desorption recombination treatment and the effect of the hydrogen pressure and temperature conditions in the disproportination step on magnetic anisotropy as well as the state of disproportionated samples was investigated. Magnetic anisotropy was maximized when the sample was hydrogen disproportionated at 30 kPa and 800 °C–820 °C. The analyses of the X-ray diffraction (XRD) patterns showed that the iron boride phase formed during the hydrogen disproportionation step crystallized in the tetragonal structure. The lattice parameters and the peak intensity of this iron boride phase in XRD patterns varied depending on the disproportionation conditions. Both magnetic anisotropy and iron boride peak intensity became stronger when the disproportionation condition was close to the boundary of disproportionation and recombination reactions. These results suggest that there is some kind of relationship between magnetic anisotropy and the state of iron boride phase in disproportionated samples. [ABSTRACT FROM AUTHOR]

A capping C layer with various thicknesses was sputtered on FePt/MoC/CrRu/glass and postannealed from 190 °C to 365 °C. The optimal magnetic property was obtained at 2 nm-thick C layer annealed at 268 °C and used to discuss an FePt thickness effect. The FePt films with a thickness of 4–10 nm were deposited on MoC/CrRu at 425 °C using magnetron sputtering. The MoC intermediate layer was epitaxially grown on the (200) textured CrRu seed layer, and the FePt film was prepared on the (200) textured MoC at 425 °C. The FePt film shows strong (001) texture, and the out-of-plane coercivity of 7.5 kOe has been demonstrated in 10 nm-thick FePt film. After capping a 2 nm-thick C layer and postannealed at 268 °C, the out-of-plane coercivity was increased to 10 kOe compared with FePt without C capping. From microstructure, the FePt grains were distributed in- or between-islandlike structure and further separated by excess carbon from a capping carbon layer and an MoC intermediate layer. [ABSTRACT FROM AUTHOR]

The magnetic domain motion with varying magnetic field is investigated by magneto-optic Kerr microscopy on a slightly Goss misoriented Fe–Ga rolled sheet, and a close relationship between the magnetostriction and the domain motion is reported during the magnetization process. Along the rolling direction (RD), a high magnetostriction value \lambda \mathrm { {//}} of 281 ppm is observed under no prestress for the sheet. The magnetic domains on the \sim 12^\circ misoriented Fe–Ga (110) surface appear in the lancet shape and align as lancet comb structures. The lancet domain motion on the surface well explains the magnetostrictive performance \lambda \mathrm { {//}} with the consideration of 90° domains within the lancet structure. The rapid increase of magnetostriction is attributed to the quick motion of 90° domains within the lancet structure under the field below $70\sim 100$ Oe. Under the higher magnetic field, these lancet domains gradually disappear with the field increasing, accompanied with the approach to the saturation magnetostriction along the RD. [ABSTRACT FROM AUTHOR]

The electrical resistance is one of the important properties for Nd2Fe14B magnets with low eddy-current loss. We have coated Nd–Fe–B melt-spun particles with CaF2 by the liquid-phase coating technique and then performed hot-pressing and hot-deformation to make Nd2Fe14B/CaF2 composite magnets. The morphology and distribution of CaF2 in the magnets and its influence on the coercivity mechanism and the electrical properties of the Nd2Fe14B/CaF2 magnets have been investigated by scanning electron microscope, hysteresisgraph, and four-probe resistivity meter. The morphology of CaF2 depended on the liquid-phase synthesis parameters, especially the concentrations of the reactants. On the surface of Nd–Fe–B particles, there formed only a few CaF2 nanoparticles and nanoflakes when 0.5 and 1 mol/l reactant aqueous solutions were used as precursors. With the increase of the concentrations of the reactants, there obtained a flake-shaped thin CaF2 coating on the Nd–Fe–B particles. In addition, the CaF2 coating became thicker, $\sim 150$ –200 nm, with further increasing the concentrations of the reactants to 2 mol/l. After compaction and hot-deformation, the electrical resistances of the Nd2Fe14B/CaF2 magnets fabricated using the concentrations of the reactants of 2 mol/l reached approximately 580 $\mu \Omega $ cm, which increased about 348% comparing with the corresponding pure Nd–Fe–B magnet. It is interesting to find that the coercivity of the Nd2Fe14B/CaF2 composite magnets increased from 12.42 to 13.5 kOe when the concentrations of the reactants increased from 0.5 to 1.5 mol/l and then decreased to 10.2 kOe with further increasing the concentrations of the reactants to 2 mol/l. The reason for the increment of coercivity may be that CaF2 nanoparticles and nanoflakes acted like lubricants that were beneficial to the rotation and the orientation of Nd2Fe14B particles during the hot-deformation process. [ABSTRACT FROM AUTHOR]