Interlayer interactions in FeNi/Bi/FeNi trilayers

Interlayer interactions in FeNi/Bi/FeNi films are studied experimentally. It is established by SQUID magnetometry and magnetic resonance investigations that the interlayer interaction in these films is determined by the bismuth spacer thickness and temperature. A giant magnetoresistance effect is observed in the investigated trilayers.     

Magnetic resonance studies of three-layer FeNi/Bi/FeNi films

The interlayer coupling in three-layer FeNi/Bi/FeNi films is studied by electron magnetic resonance. The magnetic anisotropy at the permalloy–bismuth interface is shown to play a significant role in the formation of the magnetic state of the film structure. The interlayer coupling oscillation period is found to be about 8 nm. The interlayer coupling and the interface anisotropy and their temperature dependences are determined.     

Magnetic properties, complex permittivity and permeability of FeNi nanoparticles and FeNi/AlO x nanocapsules

Structures, surface composition, magnetic properties, and electromagnetic properties of FeNi nanoparticles and FeNi/AlO _x nanocapsules were investigated. The compositions of these nanoparticles/nanocapsules were found to be quite different from those of the corresponding targets. Al atoms could promote the evaporation of Fe atoms and suppress the evaporation of Ni atoms in the arc discharge process. The protective AlO _x shell can effectively increase the resistivity of FeNi nanocapsules and suppress the growth of FeNi nanoparticles and reduce their magnetization. For FeNi nanoparticles/nanocapsules, the same natural resonance appearing at 6.4 GHz originates mainly from magnetic FeNi cores. FeNi nanoparticles/nanocapsules exhibit promising possibility for application as a new type of electromagnetic wave shield/absorbent.     

Low-Temperature Magnetization Switching of Bilayer FeNi/FeMn Films

Journal of Experimental and Theoretical Physics - A change in the kinetics of magnetization reversal of a bilayer ferromagnet–antiferromagnet film during a decrease in the temperature is...     

Optical and magnetooptical characterization of FeNi/Cu multilayers

A series of [FeNi(1.7 nm)/Cu(t_Cu)]₃₀/Fe(10 nm) multilayers with the range of t_Cu from 0.36nm to 4.32nm deposited on glass substrates was studied by measuring the effective optical constants n and k, saturation magnetooptical polar Kerr rotation θ _k and ellipticity η_k and evaluating the effective complex off-diagonal elements of the dielectric tensor ε _xy ^′ and ε _xy ^″ . It was found that the four primary quantities ε _xy ^′ , ε _xy ^″ , n and k vary concurrently with respect to t_Cu, while the dependences of θ _k and η _k on t_Cu differ drastically. To explain this difference the contributions of both the real and imaginary parts of the off- diagonal dielectric tensor elements and the effect of complex optical constants have to be considered. No obvious correlation was found between the variation of ñ, ε~ _xy and the oscillations of GMR of the multilayers.     

Spin-Wave Modes in Exchange-Coupled FePt/FeNi Bilayer Films

A simple magnetic modulation structure of the exchange-coupling FePt/FeNi bilayer film is fabricated and studied for its magnetization dynamics using time-resolved magneto-optical polar Kerr spectroscopy. It is found that two spin-wave modes can be excited. One is fixed at -3.2 GHz in frequency for any external field and may serve as a frequency-stabilized spin-wave filter, while the other is external field dependent. In contrast, only the external field-dependent mode is excited in single-layer FeNi, supporting the localized origin of the mode at -3.2 GHz, which is confined to a thin exchange-coupling region. The other external field-dependent mode in frequency is attributed to the Kittel mode.     

Asymmetrically shaped hysteresis loop in exchange-biased FeNi/FeMn film

The magnetization reversal of the bilayer polycrystalline FeNi(50 Å)/FeMn(50 Å) film sputtered in a magnetic field has been studied by magnetic and magneto-optical techniques. The external magnetic fields were applied along the easy or hard magnetization axis of the ferromagnetic permalloy layer. The asymmetry of hysteresis loop has been found. Appreciable asymmetry and the exchange bias were observed only in the field applied along the easy axis. The specific features of magnetization reversal were explained within the phenomenological model that involves high-order exchange anisotropy and misalignment of the easy axes of the antiferromagnetic and ferromagnetic layers. It has been shown that the film can exist in one of three equilibrium magnetic states in the field applied along the easy axis. The transitions between these states occur as first-order phase transitions. The observed hysteresis loop asymmetry is related to the existence of the metastable state.     

Pulsed inductive microwave magnetometer response calculated for IrMn/FeNi bilayers

Micromagnetic simulations of a pulsed inductive microwave magnetometer (PIMM) experiment are performed using a well established model for exchange bias. The model (Interacting Grain Model) consists of ferromagnetic grains and antiferromagnetic grains with randomly distributed easy axes. A perfectly compensated interface between the ferromagnet and the antiferromagnet is assumed which leads to spin flop coupling. The antiferromagnetic layer is modelled as two totally antiparallel sublattices with a small intergrain exchange between each antiferromagnetic sublattice. Simulations of an experimental PIMM setup provide a shift of the minimum of the resonance frequency which is also observered experimentally.     

Hysteretic behavior of angular dependence of exchange bias in FeNi/FeMn bilayers

For FeNi/FeMn bilayers, the angular dependence of exchange bias shows hysteresis between clockwise and counterclockwise rotations, as a new signature. The hysteresis decreases for thick antiferromagnet layers. Calculations have clearly shown that the orientation of antiferromagnet spins also exhibits hysteresis between clockwise and counterclockwise rotations. This furnishes an interpretation of the macroscopic behavior of the ferromagnetic layer in terms of the thermally driven evolution of the magnetic state of the antiferromagnet layer.     

Ion beam mixing of FeNi3 multilayers

An Fe/Ni multilayer of overall FeNi₃ composition, prepared by Joule effect deposition, has been irradiated with 200 keV krypton ions at a nominal dose of 5×10¹⁵ions/cm² to induce mixing at the interface. Depth profiling AES, RBS, XRD (glancing angle) and CEMS have been used to characterize the samples before and after irradiation and also after subsequent mild annealing. In the final structure, we have recognized the presence of embryos of an ordered FeNi₃ superlattice.     

The effects of Co-metal clusters on exchange bias for Co-doped NiO/FeNi bilayers

Co-doped NiO inhomogeneous films were synthesized by sputtering metallic Co chips and NiO together and the exchange bias of bilayers Co-doped NiO/FeNi was investigated. When Co content was up to 25.2%, the exchange bias field H_E at the room temperature increased to the maximum which was about three times compared to the undoped-bilayers. With further increase of Co content, the exchange bias field H_E and blocking temperature T_B decreased. Analysis suggests that the configuration of nanometer-sized Co-metal clusters enchased into NiO matrix played an important role in the change of magnetic behavior for the bilayers.     

FeCuNbSiB对FeNi/PZT复合结构磁电效应的影响

构造了FeCuNbSiB/FeNi/PZT磁电复合结构并与FeNi/PZT复合结构进行了对比研究.分析了高磁导率材料FeCuNbSiB对FeNi磁场的影响机理,研究了FeCuNbSiB/FeNi/PZT三相复合结构的磁电效应.实验表明,在FeNi/PZT两相层合结构中黏接FeCuNbSiB层后:1)最优偏置磁场从200 Oe降低到55 Oe,最大谐振磁电电压系数从1.59 V/Oe增大到2.77 V/Oe;2)在低偏置磁场中,层合结构磁电电压转换系数提高了1.7—7.8倍;3)层合结构的磁电电压对静态磁场 关键词： 层合结构 最优偏置磁场 高磁导率 磁电电压转换系数     

Effect of the Semiconductor Spacer on Positive Exchange Bias in the CoNi/Si/FeNi Three-Layer Structure

JETP Letters - Films consisting of a hard magnetic ferromagnet CoNi and a soft magnetic ferromagnet FeNi interacting through a nonmagnetic Si semiconductor spacer are experimentally studied. The...     

Finite-temperature theory of local environment effect in FeNi alloy

Finite-temperature theory of local environment effect (LEE) is extended by taking account of the LEE on the amplitude of the local magnetic moments. By use of the improved theory, the finite-temperature magnetism of FeNi alloy is investigated in detail. Distribution of thermally averaged local moments due to the randomness of the atomic configuration are obtained. The magnetization and the internal-field distribution are calculated from them. Present theory explains well the rapid deviation from the Slater-Pauling curve, the downward deviation from the Brillouin curve and the broad internal-field distribution seen by ⁵⁷Fe. In these phenomena the broad distribution of Fe local moments due to the LEE is important.     

A model for magnetic abnormalies of FeNi Invar alloys

A model based on the idea of localized magnetic moments is presented which allows to calculate the local magnetic moment expectation values of FeNi alloys. The only parameters of the model are the exchange integralsJ _FeFe,J _FeNi,J _NiNi. By assuming a “mixed” exchange interaction the concentration dependence of the exchange integralsJ _FeFe andJ _FeNi is calculated. The model allows the iron magnetic moments to orient parallel or antiparallel to the magnetization axis, depending on the local environment. It explains the magnetic abnormalies of FeNi Invar alloys as for example the concentration dependence of the mean magnetic moment and the Curie temperatures as well as the characteristic “flat” courves of the spontaneous magnetization.     

Tunable resonance frequency of FeNi films by oblique sputtering

FeNi thin films were fabricated by radio frequency magnetron sputtering on Si(1 1 1). Dynamic properties at remanence of the films were systematically investigated in a wide frequency range from 100 MHz to 5 GHz. The results show that both thickness of FeNi films and oblique angle have important effects on the magnetic properties of the films, the magnetic resonant frequency of the films can also be adjusted by the two factors. The in-plane uniaxial magnetic anisotropy field can be adjusted from 82 Oe to 220 Oe by increasing the oblique angle. As a consequence, the magnetic resonant frequency of the films increased from 2.7 GHz to 4.2 GHz.     

铁镍合金纳米管阵列的模板制备和磁性

"在阳极氧化铝模板的孔洞中利用模板浸润的方法成功制备出了铁镍合金纳米管阵列．通过改变所用模板的参数和沉积纳米管的的制备条件,所制备的纳米管的长度、内径和外径的尺寸都可以得到有效控制．利用扫描电子显微镜和透射电子显微镜对所制备的纳米管及其阵列的形貌进行了表征．对铁镍合金纳米管阵列的宏观磁性测量表明样品具有磁各向异性,沿纳米管长轴方向样品更容易被磁化．对纳米管的磁化反转机制和磁矩在纳米管中的静态分布进行了讨论．铁镍合金纳米管的这些性质都是由纳米管的独特结构造成的．"     

Magnetoresistance Detection of Vortex Domain in a Notched FeNi Nanowire

Revealing the physical nature of vortex wall(VW) behavior in magnetic nanostructures has been of great importance for future device concepts. Here we introduce the superior properties of VW in a notched FeNi nanowire under the action of an electronic current. The pinning-dependent VW propagation is demonstrated by a successive in-field magnetic force microscopy, an anisotropic magnetoresistance measurement, as well as micromagnetics.Based on the developed method, the propagation of VW can be effectively captured by monitoring the change of magnetoresistance in the FeNi nanowire, which sheds light on the development of future spin-based devices.