Shiro Kambe

Magnetic Sensor Using Second Harmonic Change in Magneto-Impedance Effect

This study reports on a magnetic sensor composed of a Cu wire sandwiched between Co-based amorphous ribbons. The impedance of the Cu wire largely depends on the permeability of the amorphous ribbons and changes with an external field. This phenomenon results in a change in the voltage at the fundamental frequency (V1st) and that at the second harmonic frequency (V2nd) at both ends of the Cu wire. The maximum V2nd variation rate was ~150%/Oe which is about 15 times larger than that of V1st. The detection of the second harmonic voltage offers the potential for a great improvement in the magnetic field sensitivity.

Superconductive transition at 39.0K in (Bi, Pb)2(Sr, La)2CuOy

Abstract Bi 1.6 Pb 0.4 Sr 1.6 La 0.4 CuO y superconductor with the basic structure of Bi 2 Sr 2 CuO 6 (2201 phase) was prepared by annealing in the absence of oxygen. A high Tc value of 39.0K was observed. This result indicates that the 2201 phase in the Bi system gas an equal potential for high Tc to (La,Sr) 2 CuO 4 does.

Origin of modulated structure for high-Tc Bi2212 superconductor

Abstract The high-Tc superconductor Bi2Sr2CaCu2Oy is known to have modulated structure. We have systematically investigated modulation period, lattice mismatch, oxygen content and Bi valence and made clear the origin of modulation. The lattice mismatch between the CuO2 plane and the BiO block is relaxed by expanding the BiO block. The expansion is brought about by both insertion of oxygen into the BiO block and a change in Bi valence. The insertion of oxygen leads to formation of the modulation. The decrease in Bi valence leads to the increase in the ionic radius of the Bi.

Structure of Ba2InCuOy: A new layered cuprate with a blocking layer of BaInOy perovskite

Abstract A new blocking layer with an a -axis length of 4.18 A, BaInO y , was found. The blocking layer supplies an apical oxygen to the CuO 2 layer and produces an oxygen vacancy in the in-plane of the CuO 2 layer. By matching the blocking layer with the CuO 2 layer, a new layered cuprate, Ba 2 InCuO 4.53 , was prepared. Its space group was Pmmm with lattice parameters of a=4.1820(6) A , b=4.1820(5) A and c=8.0889(9) A . The fact that the a - and b -axis lengths of Ba 2 InCuO 4.53 compound are much longer than those of the other cuprate compounds is explained by the existence of an oxygen vacancy in the CuO 2 layer. Its resistivity at room temperature was as large as 28.8 MΩcm. The insulating property probably comes from the existence of the oxygen vacancy in the CuO 2 layer.

Superconductive property of Bi2−2xPb2xSr2Can−1CunOy

Abstract Hole concentration of the system can be controlled by the substitution of Pb for Bi in Bi 2 Sr 2 Ca n −1 Cu n O y . Bi 2−2 x Pb 2 x Sr 2 Ca n −1 Cu n O y where x = 0.3 has the effect that T c decreases from 80 K to 75 K in the n = 2 phase. In the n = 3 phase T c was not affected. Difference in the effect of the hole concentration C hole on T c can be explained by the fact that Δ T c /Δ C hole for the n = 2 and 3 phases was different and that the value for the n = 3 phase was almost zero in the observed region.

Effect of S, Se and Te addition on the superconductive properties of Ba2YCu3O7−y

An addition of a small amount of sulfur or selenium in Ba2YCu3O7-y lead to the formation of the phase whose c-axis was 11.62 A, which is much shorter than that observed in sulfur-free Ba2YCu3O7-y. This phase increased the Tc(zero) value, accompanied by the sharpening of the transition width within 1 K.

Dramatic changes in the Bi and Cu valences of Bi 2201 phase annealing in absence of oxygen

Abstract The observed changes in the value of T c in the Bi 2201 phase are discussed in connection with the total valence of the system, Bi and Cu valence, and its lattice structure. Annealing the Bi 2201 phase, in the absence of oxygen (in N 2 or in Ar) leads to an increase of T c from 26.1–26.7 K to 31.2–39.0 K. It is proposed that the transformation of the position of oxygen atoms causes a change in the distribution of the total valence between the Bi-O layer and CuO 2 layer, which leads to an increase in T c .

Application of Fe-based nanocrystalline ribbon as a noise filter

The paper describes the application of Fe-based nanocrystalline ribbon to a common-mode noise filter in the 1 MHz/spl sim/1 GHz frequency range. A 10 /spl mu/m thick Fe-based amorphous ribbon was converted into an Fe-based nanocrystalline ribbon by annealing it at 550/spl deg/C for 10 min. The ribbon exhibited high permeability and high impedance characteristics when it was annealed in a transverse magnetic field. The resistance of a 5 mm diameter roll of Fe-nanocrystalline ribbon (12.5 mm wide and 6 cm long) increased from 3 /spl Omega/ at 1 MHz to 10 /spl Omega/ at 1 GHz. We confirmed that this filter exhibited the same noise attenuation as a conventional filter (ferrite core) but with 1/33rd its volume.

Addition of Ag, Pb, K, or Li to Bi2Sr2CaCu2Oy whisker

Abstract In order to examine the growth mechanism of a Bi2Sr2 CaCu2Oy (Bi2212) superconducting whisker, such elements as Ag, Pb, K, and Li were added to the Bi2212 powder in the molar ratio of 0.2 together with changes in sintering temperature. Potassium addition and sintering temperature at 865 °C achieved the fastest growth rate of the whisker. By varying the added elements, the diameter of whiskers is controllable. An Arrhenius plot of the growth rate of Bi2212 whiskers drew a straight line, indicating that its growth mechanism is correlated with the vapor–liquid–solid growth mechanism.

Preparation of [111] -oriented CaO film through dehydration of a Ca(OH)2film

Abstract We successfully prepared [111]-oriented CaO films through deposition of a Ca(OH)2 film by a laser ablation method, followed by dehydration of the film. It should be noted that only [100]-oriented CaO film is formed by direct ablation of a calcium oxide target. The inplane orientation of the [111]-oriented CaO thin film was random as is the case of the calcium hydroxide film. The shrinkage of the thickness from calcium hydroxide to calcium oxide agreed very well with the calculated value, clearly indicating that calcium oxide is formed from calcium hydroxide by a topotaxy mechanism.