Near-zero Magnetostriction Research Articles

ChemInform Abstract: Kinetic and Structural Aspects of Magnetic Phenomena in Amorphous Soft Ferromagnets

Abstract Some recent results concerning domain structure and domain-wall motion in amorphous soft ferromagnets are reviewed. The effect of the value of the saturation magnetostriction is discussed, with particular emphasis on the change in sign of λs induced in nearly-zero magnetostriction alloys by large tensile stresses. The ‘fast’ permeability relaxation observed during high-frequency domain-wall motion is explained in terms of a domain-wall instability under extreme velocity conditions. Finally, the unique kinetic features of the slow relaxation (after-effect) of the initial magnetic permeability will be outlined. A specific experiment, conceived to check the assumptions of the model established for this relaxation process, is proposed and discussed in detail.

Kinetic and structural aspects of magnetic phenomena in amorphous soft ferromagnets

Abstract Some recent results concerning domain structure and domain-wall motion in amorphous soft ferromagnets are reviewed. The effect of the value of the saturation magnetostriction is discussed, with particular emphasis on the change in sign of λs induced in nearly-zero magnetostriction alloys by large tensile stresses. The ‘fast’ permeability relaxation observed during high-frequency domain-wall motion is explained in terms of a domain-wall instability under extreme velocity conditions. Finally, the unique kinetic features of the slow relaxation (after-effect) of the initial magnetic permeability will be outlined. A specific experiment, conceived to check the assumptions of the model established for this relaxation process, is proposed and discussed in detail.

CoZrRe amorphous film heads for high-density magnetic recording

CoZrRe amorphous film heads with superior performance have been developed for use in high-density magnetic recording. These films produce near-zero magnetostriction of less than +2.5*10/sup -7/ and saturation magnetization of 1.2 T. It is found that the addition of a small amount of Re to CoZr markedly improves the stability of magnetic properties during head fabrication. However, the process temperature must be less than 200 degrees C. To realize the required temperature, a dry process is developed, using sputtered SiO/sub 2/ films for insulation instead of conventional hard-cured photoresist. A maximum process temperature of about 150 degrees C is obtained As a result, a high linear density of more than 2100 fr/mm (53 kfci) at a spacing of 0.1 mu m is achieved using CoZrRe film heads and metal-sputtered media with a coercivity of 1300 Oe.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Zero magnetostriction iron films

Iron films with low coercive force and near-zero magnetostriction have been prepared by ion beam sputtering. With an increase in Ar ion acceleration voltage, the dominant crystalline orientation of the films changed from the [100] to the [110] plane. The saturation magnetostriction constant, lambda /sub s/, changed from positive to negative values, corresponding to the orientation change. The lambda /sub s/ of annealed films, whose lattice constants agreed well with those of the bulk, were close to the calculated values. The coercive force had a minimum of about 2 Oe near zero lambda /sub s/. The results indicate that the soft magnetic properties of iron films can be improved by reducing lambda /sub s/, which in turn is controlled by the acceleration voltage of the ion-beam-sputtering system. >

Physical and electro-chemical properties of high rate ion-beam sputtered Fe films

Magnetic properties, resistivity, hardness, and corrosion resistance of nitrogen-doped iron films deposited using an ion-beam sputter system are reported. It was found that longer ion source idling time and higher nitrogen doping generates films with lower coercivities, lower anisotropy fields, and finer grain size for nitrogen concentration less than 3 at.%. The nitrogen in the films is chemically bonded to iron with photoelectron binding energy of 397.2 eV. For nitrogen concentrations >or=5 at.%, near-zero saturation magnetostriction, fine grain size, high saturation magnetization, 60 mu Omega -cm resistivity, 20 GPa hardness, and corrosion resistance higher than that of NiFe were obtained. >

Near-zero magnetostriction NiFe films deposited by ion beam sputtering

Near-zero magnetostriction permalloy films, 3000A thick, were made by ion beam sputtering with a Ni 80 Fe 20 target. The placing of a Ni strip onto the target and N 2 addition were used to independently adjust the film composition and crystalline texture respectively. Film composition and crystalline texture were investigated using X-ray fluorescence and diffraction. A change of the magnetostriction constant λ expressed in terms of ΔH k , obtained by straining the film, was also observed after a 250°C easy axis annealing in a vacuum oven. We suggest that this change may be related to an observed change in microstructure of the NiFe for low and a reduction of the I 200 /I 111 X-ray peak intensity ratio for high N 2 partial pressures.

Glassy metal alloys with perminvar characteristics

A number of glassy metal alloys with near-zero magnetostriction have been found to exhibit perminvarlike properties of relatively constant permeability at low magnetic fields and constricted B-H loops. A wide variety of perminvar properties can be obtained by varying heat-treatment conditions and the compositions of the materials. The low field permeability and dc coercivity of the glassy alloy perminvars can range between about 600 and 90 000 and between about 0.2 and 12 A/m, respectively. The magnetic shock problem associated with the crystalline perminvars is absent in these materials.

Magnetic Properties of Fe¿Al¿Si Sputtered Films

Whereas Fe-Al-Si film of composition 5.5 percent Al-9.5 percent Si-remainder Fe (Sendust composition range) has a high permeability and good soft magnetic properties, the sensitivity of the latter to composition changes presents difficulties as regards film formation. The authors studied another promising composition range, 2.5 percent Al-5.5 percent Si-remainder Fe, sputtering films in this range on quartz substrates. Films obtained had smaller coercivities than Sendust films, near-zero magnetostriction, similar to Sendust, and a large in-plane uniaxial anisotropy. This composition borders on a disordered and an ordered phase, suggesting that film properties may be influenced greatly by annealing and other treatment.

Determination of internal stresses distribution for a nearly-zero magnetostriction amorphous alloy

Surface and bulk magnetization curves have been measured by means of the magneto-optic Kerr effect and the conventional induction method, respectively, for the Metglas 2705 M alloy. From the analysis of the experimental measurements and using a simplified model, the angular and intensity distributions of the internal stresses have been evaluated.

パーマロイ薄膜の保磁力と磁気抵抗効果に及ぼす蒸着時真空度の影響

The effects of vacuum pressure on the coercivity and magnetoresistivity of thin permalloy films during the deposition process were investigated. Samples of permalloy films ranging in thickness between 15 and 300 nm were deposited on a glass substrate by the electron beam method under a 10−4-10−6 Pa vacuum. The substrate temperature was 573 K, and the composition of the permalloy films was Ni-19 mass%Fe with near-zero magnetostriction. The average electrical resistivity (ρa) of permalloy films during deposition decreases, as vacuum pressure is decreased and film thickness is increased. However, since the change in magnetoresistivity (Δρ) is independent of vacuum pressure and film thickness, the magnetoresistivity ratio (Δρ⁄ρa) increases, as pressure is decreased and thickness is increased. On the other hand, the coercivity (Hc) and the magnetic anisotropy field (Hk) increase, as vacuum pressure is decreased. Moreover, the Hc and Hk peak at a thickness of nearly 70 nm. Through transmission electron microscopy, it is observed that the grain size in permalloy films increases as vacuum pressure is decreased. Auger analysis indicates that the concentration of oxygen in permalloy films decreases as vacuum pressure is decreased. These results suggest that the decrease in ρa and the increase in Hc under high vacuum are attributed to the decrease in oxygen and the grain growth in permalloy films.