The induced uniaxial anisotropy field Hk in very thin Ni79Fe21 films, sandwiched by seed and protective Ta layers, was investigated. Films prepared by using a UHV sputtering process show a very sharp fiber texture of fcc-<111> even with a film thickness of 3 nm. The Hk value was found to decrease as the film thickness decreases below 20 nm, even after an annealing procedure in a magnetic field. The change in the induced anisotropy energy Ku was measured as a function of the temperature while applying a dc magnetic field parallel to the hard axis of magnetization. The value of Ku of as-deposited thin films decreases significantly with increasing temperature from 50°C to 100°C. The Ku reduction in a film of 5 nm reaches ∼40% of that of the original value. It is likely that the Ku reduction at temperatures below 100°C is mainly caused by alignment of atom pairs at film surfaces. The thickness of film surfaces with highly mobile atoms was estimated to be 5-6 A. The high mobility of surface atoms may disrupt the alignment of atom-pairs parallel to the field direction during the film deposition and annealing process, resulting in the smaller Hk of very thin films.
A transcutaneous electric transmission system (TETS) is effective for an artificial sphincter utilizing SMA (Shape Memory Alloy) in a small implanted device driven by heating, as a contactless method that does not require code etc. in order to drive the implanted device. We examined TETS with a joule heat of resistance attached to the SMA in order to heat the SMA. We examined a temperature control system that tracks the electric power transmission system as we create heating.
An X-Y linear induction motor (X-Y LIM) is a structure having two windings in the horizontal x - and y - axis directions. Exciting one winding generates a one-directional thrust, and a two-dimensional drive becomes possible by exciting two windings at the same time. We investigated only one pole of an X-Y LIM having a three-phase, five-pole structure, and we used a three-dimensional finite element method as the analytical technique. The following characteristics were examined to obtain guidelines for future designs: (1) magnetic flux density and starting thrust with respect to primary current; (2) magnetic flux density and starting thrust with respect to gap; (3) magnetic flux density and starting thrust with respect to aperture ratio; and (4) magnetic flux density and starting thrust with respect to yoke thickness.
This paper presents a fatigue evaluation of steel plates based on chaotic attractors of Barkhausen noise. The fatigue and degradation of magnetic materials affect the magnetic domain. Hence these can be evaluated by Barkhausen noise. Barkhausen noise from magnetic materials is a very complicated wave. Thus we need a special evaluation method to use it. The quantitative change of Barkhausen noise after a fatigue stress test can be found by the fractal dimension of the chaotic attractors constructed by the measured Barkhausen noise.
We designed and fabricated cylindrical magnetic ac markers for magnetic motion capture system. The ac marker is 12 mm long and 7 mm in diameter. The inductance of the coil was calculated using Dwight’s formula. A magnetic field of 2.4 × 10-7 Oe was measured using a high-frequency carrier type thin-film magnetic field sensor combined with a carrier-suppressing circuit. The distance detected between sensors and marker was 1250 mm.
This paper discusses a ferro/antiferro exchange coupled, high-frequency carrier-type, thin-film magnetic field sensor which can obtain an asymmetrical applied field dependence of the impedance of the sensor element due to the unidirectional anisotropy. We fabricated a sensor element that consisted of 200-nm-thick NiFe and 30-nm-thick FeMn films. We verified that the NiFe/FeMn bilayer structure was necessary for an asymmetrical high-sensitivity output. An exchange-coupling field of 145 A/m and an asymmetrical impedance change were obtained.
We developed a thin-film electromagnet, which constitues a micromachine. The thin-film electromagnet consists of a planar coil and magnetic material. To make an efficient electromagnet, we analyzed the magnetic field by the computer simulations using the finite-element method. As a result, we found that a magnetic thin-film placed under the planar coil creates a more efficient magnetic field than a magnetic core placed at the center of the planar coil. The thickness of the magnetic thin-film, or of the insulator between the planar coil and magnetic thin-film, does not affect the magnetic field so strongly. We then made a thin-film electromagnet using an integrated circuit fabrication process and used it to drive a micro-mirror. We found that it can drive the micro-mirror with 100-mA current at its resonance frequency, 923 Hz.