Magnetic Properties Of NiFe Films Research Articles

Tunable high-frequency magnetic properties of NiFe films on triangular wave-like surface of Al2O3 substrate

To tune high-frequency properties, NiFe films are fabricated on triangular wave-like surface of Al2O3 substrate by magnetron sputtering. Faceting, the transformation of a planar surface into two or more surfaces, can be observed on m-plane Al2O3 substrate via annealing process and further format the continuous periodic triangular wave-like structure. The wavelength and oscillation can be adjusted by annealing temperature and time. The magnetic anisotropy field (Hk) of the magnetic film is increased to 320 Oe and the resonance frequency (fr) also has a big improvement to 5.4 GHz. These changes are mainly attributed to the dipolar interaction between surface magnetic charges in the studied system. We prove that high-frequency properties of the soft magnetic film can be controlled by designing a nanoscale periodic triangular wave-like morphology on film surface.

Effect of a CoFeB layer on the anisotropic magnetoresistance of Ta/CoFeB/MgO/NiFe/MgO/CoFeB/Ta films

The anisotropic magnetoresistance (AMR) and magnetic properties of NiFe films can be remarkably enhanced via CoFeB layer. In the case of an ultrathin NiFe film having a Ta/CoFeB/MgO/NiFe/MgO/CoFeB/Ta structure, the CoFeB/MgO layers suppressed the formation of magnetic dead layers and the interdiffusions and interface reactions between the NiFe and Ta layers. The AMR reached a maximum value of 3.56% at 450°C. More importantly, a single NiFe (111) peak can be formed resulting in higher AMR values for films having CoFeB layer. This enhanced AMR also originated from the significant specular reflection of electrons owing to the crystalline MgO layer, together with the sharp interfaces with the NiFe layer. These factors together resulted in higher AMR and improved magnetic properties.

Influence of Thickness on Magnetic Properties of Electrolytic Ni-Fe Films Deposited on Cu Wires

The influence of film thickness on magnetic properties of Ni-Fe films electroplated under tensile stress on 50 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu{\rm m}$</tex></formula> Cu wires is investigated by means of hysteresis loops, FMR (ferromagnetic resonance) and MI (magnetoimpedance) measurements. With increasing thickness the coercive force and the remanence ratio decrease. The MI and network analyzer-FMR (NA-FMR) measurements indicate the presence of a strong uniaxial anisotropy along the wire axis in the thin films. With increasing film thickness the anisotropy gradually changes to the hard-wire-axis anisotropy. While the hard-axis anisotropy of thick films can be ascribed to the magnetoelastic coupling with the compressive back-stresses in the Ni-Fe layer, the easy-axis anisotropy of thin films is probably due to the surface anisotropy at the Ni-Fe/Cu interface.

Topographic anisotropy in continuous magnetic films with two-dimensional surface nanomodulation

Artificial and local control of spin-configuration in nanoscale in continuous magnetic films could enable new spin-based electronics and precision sensor technologies. Extensive theoretical research has recently been devoted to examination of surface nanovariation mediated magnetism and its utility, which has been demonstrated only in one-dimensional surface modulation. However, a realization of engineered spin configuration using two-dimensional (2D) nanomodulation is limited by local vortex formation induced by magnetostatic energy. In this work we demonstrate for the first time, an ability to control the anisotropy in continuous magnetic films by periodic surface nanomodulation in two-dimensions (2D). Magnetic properties of NiFe films with nanomodulated surfaces have been studied as a function of both film thickness and modulation amplitude. For films with a patterned square array (without breaking the film continuity), a clear fourfold symmetry of anisotropy field and coercivity was observed with rotation angle. An experimental phase diagram of anisotropy with respect to film thickness and modulation amplitude has been produced which delineates that the observed fourfold anisotropy is induced by the magnetostatic effect. The observed dependence of anisotropy field on film thickness and surface modulation amplitude agrees well with the developed theory.

Magnetic properties of Ni-Fe films prepared by a DC triode sputtering method

The magnetic properties of Ni-Fe films with 81-wt.% Ni prepared by a DC triode sputtering method are studied as functions of sputtering parameters. Two kinds of substrates are used: one is flat and the other is patterned. In the former case sufficiently low coercive forces are obtained when both the target voltage and the Ar pressure are kept below the critical values. In the latter case, a negative substrate bias voltage is necessary to improve the magnetic properties in addition to the previous conditions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Magnetic properties of NiFe films prepared using ion-beam sputtering

The magnetic properties of NiFe films in the thickness range of 1 to 3 μm prepared using ion-beam sputtering were investigated by varying parameters such as the grid system, composition ratio of the targets, accelerator voltage and the beam current bombarding the substrate. The effects of the ion-assist voltage and ion-assist current on magnetic and electrical properties were investigated and the deposition conditions for NiFe films with low coercive force and resistivity were clarified. Due to their optimization of the ion-assist voltage and current, the ion-beam sputtered NiFe films have the low coercive force and resistivity necessary for thin film head applications.

The Effects of Annealing on the Grain Growth and Surface Rearrangement of Electroplated Nickel-Iron Films

Nickel-iron films were deposited on a copper-covered plastic substrate and annealed at 400, 600, 800, 1100, and 1200°C. The films were stripped from the substrate, and were thoroughly cleaned and dried before being annealed. Recent works [1, 2] have shown that the magnetic properties of Ni-Fe films are strongly dependent on grain size, and hence on the annealing treatment. The present work emphasizes the surface change of the film due to annealing.The composition of the electroplated films was kept at 80% Ni, 20% Fe; the thicknesses of the annealed samples were from 5 to 10 μ. The structure of as-plated Ni-Fe film was found to be the disordered γ phase, which is fcc. All of the films were polycrystalline with no preferred crystallographic orientation. The average grain size of the as-plated films was 300 A (Fig. 1). This did not vary much within the prescribed thickness range.

Magnetic properties of Ni-Fe films coupled with stripe-domain films

A study was made of the change in anisotropy field, coercivity, angular dispersion, and creep threshold of an ordinary Ni-Fe film when coupled with a stripe-domain film. It was found that the values of these properties all increased as a result of the coupling.

Ferromagnetic Resonance Linewidth and Internal Biasing Field in Ni-Fe Films as a Function of Dispersion in the Anisotropy Field Magnitude

Ferromagnetic resonance techniques have been used to measure the magnetic properties of Ni-Fe films in the 50–1500 Mc/sec range. Resonance was observed in the plane of films 8 mm in diameter and 600–2600 Å thick. The primary purpose of the investigation was to obtain a correlation between the resonance linewidth extrapolated to zero frequency (ΔH)0, and the dispersion in anisotropy field magnitude Δ90. The zero-frequency linewidths found were about 2.8 times the values calculated theoretically from values of anisotropy field magnitude dispersion independently obtained in this laboratory. Plots of the resonance frequency squared as a function of resonance field showed a shift, or internal bias Hi, toward positive field values as others have observed. There was little or no shift for films with Δ90 less than about 0.2, but for larger dispersion, the shift increased approximately linearly with Δ90. A very good linear correlation was found between Hi and α0, the high-frequency damping parameter. It is suggested that the internal biasing field may be associated with the magnetization rippling that Fuller and Hale and Feldtkeller have observed in electron micrographs. Also, it may be possible that the larger-than-expected values of (ΔH)0, and the wide variation in α0 values (0.006–0.03) reported here are caused by the energy loss, which Feldtkeller has termed ``ripple hysteresis,'' associated with the movement of the small-angle walls, which result from the magnetization rippling.