Yoshio Matsuo

Permeability in PLD-made Mn-Zn ferrite thin films by low-temperature process

Abstract Although a soft ferrite thin film with high resistivity is to be applied to GHz magnetic devices, a fabrication process with high temperature annealing prevents us from applying to those devices. This contribution reports that soft ferrite films with the permeability of ≈10 at the frequency of 1xa0GHz can be obtained by PLD method using low-temperature process.

Establishment of Multipole Magnetizing Method and Apparatus Using a Heating System for Nd-Fe-B Isotropic Bonded Magnets

To contribute to the size reduction of electromagnetic devices, a multipole magnetizing method for Nd-Fe-B isotropic bonded magnets using a heating system without any magnetizing power supply was examined. After rapidly heating above their Curie temperature, the magnets are magnetized during cooling in the presence of a magnetic field generated by a set of Sm-Co permanent magnets. The level of magnetization can be tailored by variation of the final temperature to which the magnets are cooled in the presence of the magnetic field. Due to the heating process, the magnets show excellent thermal stability.

Superior magnetic properties of Mn-Zn ferrite thin films prepared by low-temperature process using laser ablation technique

Mn-Zn ferrite thin films with coercive force of approximately 4 kA/m were obtained by a low-temperature process using laser-ablation technique. Thin films were prepared at substrate temperature of room temperature in Ar atmosphere with a shadow mask using glass substrates. It was found that the spinel structure is formed in the films and that the surface roughness caused by large particles is improved.

Fine pole-pitch magnetizing method for Nd–Fe–B isotropic magnet with high coercivity

Fine pole-pitch magnetization of Nd–Fe–B magnets is an important technology that contributes to miniaturization of electromagnetic devices and smaller fractional movement. However, as Nd–Fe–B magnets have a high coercivity, large amounts of energy are required for magnetization. Miniaturization of devices is associated with insufficient magnetization characteristics due to the limitations of current density. We developed a magnetization method using heating system. This method involves cooling in the magnetizing field by permanent magnets after rapid heating to temperatures above the Curie point of the Nd–Fe–B magnet. This method, which we named “ultra high magnetizing (UHM) process,” achieved greater magnetization characteristics than conventional technology. Therefore, the UHM process is a useful technology to achieve further miniaturization of electromagnetic devices.

Room temperature growth of crystalline Mn-Zn ferrite thin films by laser ablation technique

A laser ablation technique contained with a shadow mask in Ar atmosphere enables us to obtain crystalline ferrite thin films on glass substrates at room temperature. Investigations on the Ar pressure, P/sub Ar/, and the distance between the shadow mask from the target, L/sub 1/, were carried out. The optimum conditions for forming the spinel structure of Mn-Zn ferrite were P/sub A/r=20 mTorr and L/sub 1/=20 mm, respectively.

Mn–Zn ferrite thin films fabricated on crystalline substrates using laser ablation technique

We report a fabrication of Mn–Zn ferrite thin films by a low temperature process. It was found that usage of crystalline substrates is an effective way to obtain crystallized Mn–Zn ferrite thin films at the substrate temperature of room temperature in laser ablation technique. The usage of crystalline substrates reduced the coercive force of the thin films by approximately 25% compared to that of the thin films fabricated on glass substrates.

Magnetostrictive properties of Tb-Fe-Co system thin films

The magnetostrictive properties of Tb-Fe-Co system thin films are studied. The largest magnetostriction is obtained when Ar gas pressure during sputter deposition is set to 0.7 Pa. Also, the magnetostrictive properties are improved drastically with annealing process between 200/spl deg/C and 300/spl deg/C. Furthermore, it is observed that the Curie temperature of the Tb-Fe-Co film is very low but can be improved with Co ratio. The evaluation of the films is carried out using an X-ray diffractometer, electron probe micro-analysis and vibrating sample magnetometer for the structural properties, composition analysis and magnetization properties, respectively. The magnetostriction and internal stress of the film is measured using a cantilever actuator and a long-scan profile, respectively.

Highly effective, thin surface mounting type inductor

Summary form only given. In recent years there have been increasing demands for the power supplies of microprocessors to supply a high current at a low voltage while maintaining a favorable load response performance. This in turn requires inductors for use as DC-DC converters to have low winding resistance and low inductance. Consequently these inductors now incorporate many vertical-structure parts for reasons of low production costs. Assuming further miniaturization of electronic equipment and components, however, vertical parts are likely to be adversely affected by the expanding magnetic field that interlinks with the winding region. We performed magnetic field analysis on a new method of decreasing the interlinking magnetic fluxes in the winding region by improving the core structure and winding technique.

Low-bias inductors

High-speed data transmissions centering on Internet are spreading not only to corporations, schools, and government offices, but also to households at large. Asymmetric Digital Subscriber Line (ADSL) in particular is spreading rapidly in many countries due to its receptivity to existing telephone networks without requiring a new communications infrastructure. In response, we reviewed the pulse transformers used in ADSL and examined core shape optimization techniques for ADSL pulse transformers. To realize high-fidelity and wide-band transmission of signals, ADSL pulse transformers must have a low total harmonic distortion (THD) characteristic. Essential to a low THD is the linearity of dc bias (or constancy of /spl mu/ in the B-H loop). We therefore probed bias moderation factors, applying magnetic field analysis to two major core shapes, namely toroidal and EI. The results indicated that the linearity of dc bias is greatly influenced by the magnetic flux density distribution. We found that toroidal is better than EI in a weak magnetic field condition and that a smaller core thickness is better than a greater core thickness under all conditions.

Thin surface mounting type inductor and its application (high-performance inductor)

In recent years there have been increasing demands for the power supplies of microprocessors to supply a high current at a low voltage while maintaining a favorable load response performance. This in turn requires inductors for use as dc-dc converters to have low winding resistance and low inductance. Consequently, these inductors now incorporate many vertical-structure parts due to low production costs. Assuming further miniaturization of electronic equipment and components, however, vertical parts are likely to be adversely affected by the expanding magnetic field that interlinks with the winding region. We performed magnetic field analysis on a new method of decreasing the interlinking magnetic fluxes in the winding region by improving the core structure and winding technique. It was found that, by providing a number of windings on a laterally structured core and by connecting them cumulatively, the magnetic fields induced in the gap areas could be removed from the winding region. This inductor proved to yield an outstanding low-loss performance when used as a dc-dc converter for high-frequency operation.