Hideki Takeda

Giant Magnetoresistance in Bulk Cu-Rich Co–Cu, Co–Ni–Cu and Fe–Ni–Cu Granular Alloys

Magnetoresistance has been investigated for bulk Cu-rich Co–Cu and Co–Ni–Cu and Fe–Ni–Cu granular alloys prepared by aging and plastic deformation. Giant magnetoresistance (GMR) is observed in these bulk alloys in the process of phase separation and anisotropy in GMR for Fe5Ni15Cu80 alloy aged at 500° C for 170 min is obtained by compression.

Precision die-casting of optical MU/SC conversion sleeve

Abstract The performance of MU/SC conversion sleeve produced by bulk metallic glass (Zr55Al10Ni5Cu30) was examined. A precision die-casting method was applied to improve size accuracy. The size accuracy of the conversion sleeve produced by the precision die-casting method was ±1 μm, and optical insertion loss (Li) was less than 0.3 dB for a standard value. The wear resistance of metallic glass is improved by surface oxidation treatment in air at 673 K. The MU/SC conversion sleeve produced from bulk metallic glass has superior characteristics for optical parts.

GMR and micro-structure in bulk AuCo nanogranular alloys

Abstract The relation between giant magnetoresistance (GMR) and microstructure has been investigated for AuCo bulk nanogranular alloys prepared by water-quenching and subsequent aging. The GMR has been observed after aging. In particular, 12% of the magnetoresistance (MR) ratio is achieved at room temperature in the Au 85 Co 15 aged at 250°C for 100 h, which is larger than the ratio in Co Au multilayers. TheCo precipitates confirmed to be of disk-shape with 20 nm long and 0.6 nm thick with the shape of MR curve affected by TEM.

Giant magnetoresistance of CuCoX alloys produced by liquid quenching

The giant magnetoresistance (GMR) of heterogeneous Cu-Co and Cu-Co-X (X≡Mn, Fe and Ni) alloys produced by liquid quenching has been investigated. A solid solution was produced in the quenched state and fine-grained magnetic precipitates in a Cu-rich matrix were obtained by subsequent heat treatment. The Cu 85 Co 15 alloy heated at 500 o C for 90 min and quenched into water exhibits a giant magnetoresistance ratio as large as 6.3% at room temperature in a field of 15 kOe. Small amounts of Ni improve the magnetoresistance ratio. In particular the Cu 85 Co 15 Ni 5 alloy heated at 500 o C for 60 min and quenched into water exhibits a ratio of 7.6%. larger than that of the Cu 85 Co 15 alloy

Giant magnetoresistance in Au-rich Co-Au and Fe-Au bulk granular alloys

Magnetoresistance (MR) has been investigated for Au-rich Co-Au and Fe-Au bulk aged granular alloys. A negative isotropic MR is observed at room temperature. In particular, the room-temperature value of MR of 5.5% in the Co15Au85 bulk granular alloy aged at 250 degrees C for 1 h is larger than that reported for Co/Au multilayers.

The effect of aging on GMR and microstructure of Co10Cu90 ribbons

Abstract The microstructures associated with the spinodal decomposition produced by isothermal aging for Co10Cu90 ribbons are closely correlated with the giant magnetoresistance (GMR) effect. The MR ratio increases in the constant wavelength regime where the interface area increases. The decomposition occurs by longer aging, accompanying a substantial growth of particles. The MR ratio decreases with the increase in the wavelength though the field dependence of the MR ratio becomes larger in low fields. The lower isothermal aging temperature, the shorter periodic fluctuation of the composition, and accordingly the largest MR ratio of 8.1% is achieved by aging at 673 K for 166 h.

Self-injection-locked, narrow-linewidth, flashlamp-pumped Ti:Al2O3 laser

A narrow-linewidth, Q-switched, tunable Ti:Al2O3 laser, which is pumped by short-pulse flashlamps is developed using self-injection locking. By electro-optically switching the light from a second resonator consisting of a grazing incidence grating and a tuning mirror, which generates a narrow-linewidth seed pulse, to a conventional main resonator with a large volume, output energies of up to ~57 mJ/pulse were obtained with a linewidth of ~10 pm and a pulsewidth of ~20 ns. The laser was tunable within a range of 760 nm to 830 nm with high spectral purity.