The effect of magnetic field orientation on the magnetoimpedance of electroplated NiFeCo/Cu wire

Journal of Materials Science: Materials in Electronics - Giant magnetoimpedance (GMI) effect in electrodeposited NiFeCo/Cu wire is studied in the intermediate frequency region...     

Remagnetization of a circularly anisotropic amorphous wire in an alternating magnetic field

Remagnetization of an amorphous ferromagnetic wire with circular anisotropy in an alternating longitudinal magnetic field was theoretically studied within the framework of a quasistationary approximation. A frequency spectrum of the emf generated in a probing coil wound on the wire was determined, and analytical expressions describing the dependence of the emf amplitude on the alternating magnetic field amplitude H ₀ and the constant magnetic bias field value H _e were derived. The results can be applied to the development of weak magnetic field sensors.     

Enhancement of the giant magnetoimpedance effect and its magnetic response in ion-irradiated magnetic amorphous ribbons

The influences of N and Xe ion irradiation on the giant magnetoimpedance (GMI) effect and its magnetic response in Co₆₉Fe_4.5Al_1.5Si₁₀B₁₅ amorphous ribbons were systematically investigated. A large enhancement of the GMI effect and its magnetic response were achieved in N and Xe ion-irradiated amorphous ribbons. At a frequency of 3 MHz, the GMI ratio and magnetic response for an N-ion-irradiated amorphous ribbon respectively reached the highest values of 130% and 13%/Oe, while for a non-irradiated amorphous ribbon they were only about 53% and 8%/Oe. The enhancement of the GMI effect and magnetic response in the ion-irradiated amorphous ribbons resulted from the enhancement of the permeability due to rotational magnetization. Our studies indicate that low energy ion irradiation is useful for improving the magnetic softness, GMI and magnetic response of amorphous alloys, which is of practical importance for the development of high-performance magnetic sensors.     

The frequency spectrum of a voltage measured in an amorphous wire magnetized in alternating magnetic field

We have studied the process of magnetization reversal in amorphous microwires under the action of a longitudinal (axial) high-frequency magnetic field. The amplitudes of harmonics in the frequency spectrum of the response voltage between the wire ends were measured as functions of the high-frequency field amplitude and a dc axial magnetic field strength. For relatively large amplitudes of the high-frequency field, the first several harmonics in the frequency spectrum of the response voltage are highly sensitive with respect to the dc magnetic field. The experimental results are interpreted within the framework of a simple electrodynamic model.     

应力生长FeCoSiB非晶薄膜的磁各向异性研究

采用应力生长方法，制备出受压应力和张应力作用的FeCoSiB非晶磁弹性薄膜，研究了薄膜中的应变大小对FeCoSiB薄膜的磁滞回线、剩磁、应力诱导各向异性场等磁特性的影响．结果表明，无应变薄膜在薄膜面内呈现各向同性，而有应变的薄膜呈现出明显的各向异性。张应力诱导的各向异性与应力方向平行，而压应力形成垂直于应力方向的磁各向异性。各向异性场随应变的增大而线性增大。     

磁场对Ni/硅橡胶复合材料交流电导率及介电性质的影响

采用硅橡胶（110型）与金属（镍粉）按质量比为1∶2.7进行配料, 应用室温二次固化合成Ni/硅橡胶压敏复合材料样品。室温下测量了样品的压阻效应, 比较了外加0.024 T磁场前后样品的介电性质。结果表明, 当压强从3.75kPa到312.5kPa时, 样品直流电阻率下降了8个数量级。与加磁场前相比, 0.024T的磁场使得低频(40~104Hz)交流电导率提高了2.46倍, 介电常数提高了20%, 介电损耗提高了2倍, 这主要是由复合材料中铁磁绝缘体铁磁颗粒膜的隧道磁电阻效应以及磁电耦合引起的。撤去磁场后交流电导率、介电常数和介电损耗均不能回到加磁场前的初始值, 这与Ni粉的铁磁性有关。Ni/硅橡胶压敏复合材料的压阻、 磁电阻效应及磁电耦合等物理性质在磁传感器件、 信息储存等领域有潜在的应用价值。      

Effect of a strong electric field on the high-frequency properties of a helical quantum wire

New properties are predicted for a helical quantum wire (HQW) that must be manifested under the action of a constant electric field that produces a kind of quantization of the electron energy spectrum. As a result, the spectrum acquires a miniband structure inherent in quantum superlattices. The high-frequency properties of an HQW are studied. A threshold dependence of the high-frequency conductivity of the HQW on the strength of the applied constant electric field is established.     

The influence of applied tensile stress on power loss in Co-rich amorphous Co-Fe-Si-B ribbons with induced magnetic anisotropy

The influence on power loss PTof applied tensile stress σ in amorphous (Co0.89Fe0.11)72Mo3Si15B10(lambda_{s} > 0) and Co73Mo2Si15B10(lambda_{s} < 0) ribbons with different induced magnetic anisotropy Kuis reported. The losses are measured under sinusoidal flux conditions atf = 50Hz,J_{max} = 0.57T and atf = 400Hz,J_{max} = 0.10T. Measurements are carried out on samples in a stress-relieved state and with magnetic anisotropies induced by stress or field annealing. Atf = 50Hz, a minimum m Ptversus σ is observed. The σ-value (sigma_{min}) corresponding to the minimum PTincreases with increasing |Ku|. Atf = 400Hz, a minimum in PTversus σ is observed in the samples with induced magnetic anisotropy, whereassigma_{min} = 0in the stress-relieved samiales. However, no correlation between andsigma_{min}and Kuis possible from the present data.     

The measurement of the anisotropy field of cylindrical thin magnetic films

The described method for the anisotropy field measurement uses two fields HLand HT. The deviation of magnetization from the easy direction, and hence also sense signals, are proportional to these fields. The ratio of two integrated sense signals atH_{L} = 0andH_{L} neq 0reaches a certain value (∼ 2.5) with fieldH_{T} = H_{k}. In this way, Hkmay be measured by a device designed for the coercive force measurement.     

Effect of easy-plane-type surface anisotropy on domain wall assisted magnetic recording

The effect of a surface anisotropy of the easy-plane-type on the magnetic data recording in a single-crystalline film in which walls of the domain band structure play the role of information bits has been studied by micromagnetics simulations. It is established that the surface anisotropy leads to the appearance of a domain structure with the walls of different (Neél and vortex) types. Under the action of an external field, the Neél walls can be transformed into vortex walls that can be used for magnetic data recording.     

AC losses in HTS bulk and their influence on trapped magnetic field

A trapped magnetic field in a bulk is decayed and even erased by the application of an AC external magnetic field whose amplitude is much smaller than the trapped magnetic field. In the paper an analytic model to describe behavior of the trapped magnetic field is proposed assuming that its decay is caused by thermal effect due to AC losses in the bulk. The proposed model well explains AC loss characteristics, temperature rise and the decay of the trapped magnetic field of the bulk. Based on the proposed model, methods to suppress the decay of the trapped are shown and the effectiveness of the methods is shown.     

The effect of an electric field on the surface energy anisotropy in alkali metal alloys

The effect of an electric field on the surface energy anisotropy in alloys is considered for the first time with an allowance for the surface segregation.     

Effect of field annealing angle on the magnetic properties of an amorphous Fe-B-Si-C alloy

Annealing amorphous ribbons in a field in the plane at an angle to the long axis induces an easy axis also at an angle to the long axis and decreases the domain width. These effects result in a decrease in the 60-Hz losses and for domain rotations of less than approximately 5°, there is no increase in exciting voltamperes or decrease in remanence. For domain rotations of greater than about 5° the losses continue to decrease, but the exciting voltamperes increase and the remanance decreases. These effects are consistent with the domain rotation induced by the annealing.     

腐蚀对Fe基软磁材料磁性能的影响

研究了非晶和纳米晶Fe85Zr3.5Nb3.5B7Cu1软磁材料的抗腐蚀的能力以及腐蚀对纳米晶软磁材料性能的影响.非晶材料晶化后抗腐蚀能力降低,主要是由于纳米晶晶界的抗腐蚀性较差的原因.材料腐蚀后将会在其表面形成一层氧化层,从而导致软磁性能的降低,磁谱测量发现,腐蚀后的样品在较大磁场下磁化时具有两个弛豫过程,在低磁下只表现为一个弛豫过程.     

张应力对FeCoSiB非晶薄膜磁特性的影响

采用磁控溅射方法,在弯曲的玻璃基片上制备出受张应力作用的FeCoSiB非晶薄膜,研究了张应力大小对FeCoSiB薄膜的磁畴、矫顽力、剩磁、各向异性场等磁特性的影响.结果表明,薄膜的畴结构显著依赖于张应力,其磁畴宽度随张应力增加而增加;张应力导致FeCoSiB薄膜内形成较强的磁各向异性,其各向异性随应力的增大而增大.     

Hydromagnetic stability of helical flows permeated by a magnetic field with a radial component

In this paper, we have studied the linear stability of the nondissipative helical flow of an incompressible perfectly conducting fluid between two concentric cylinders permeated by a non-zero radial magnetic field. It is found that a rigidly rotating column of a perfectly conducting fluid permeated by a magnetic field [($\text{A/r}$), ($\text{C/r}$), $\text{B}{}_0$], where $\text{A, C, B}{}_0$ are constants, is stable for all infinitesimal disturbances.     

Mixed magnetooptical contrast induced by an inhomogeneous magnetic field in metal films with planar anisotropy

Magnetooptical (MO) images induced by a strongly inhomogeneous external magnetic field in magnetic metal films with planar anisotropy have been studied. In the polar Kerr effect geometry, MO images created by the normal magnetization component is observed. In the meridional Kerr effect geometry, a superposition of the MO images (mixed MO contrast) is observed, which is determined by the distribution of the normal and horizontal magnetization components. Calculation of distribution of magnetization in a film is carried out, a field of magnetic system corresponding to coordinate dependence and are simulated corresponding MO images and the corresponding MO images have been simulated, which demonstrate satisfactory agreement between the theory and experiment.     

Influence of flux penetration on magnetic field stability

When considering superconducting magnets with high stability requirements for the central induction flux, redistribution processes within the winding become important even when conductors with fine filaments are used. A model is introduced to calculate the changes of the central induction from magnet and conductor-dependent parameters. The results show good agreement, when compared with measurements.