Shoei Kataoka

Galvanomagnetic Effect of an Y–Ba–Cu–O Ceramic Superconductor and Its Application to Magnetic Sensors

The galvanomagnetic effect of a ceramic superconductor Y1Ba2Cu3O7-x was measured. It was found that when a magnetic field of a certain small value applied, the electric resistance of this material suddenly increases very rapidly from zero with increases in the applied magnetic field. The magnetic field at which the resistance appears is controllable by changing the magnitude of a current through the material. This effect is characterized by a very high magnetic sensitivity at low magnetic field. This is quite useful as a highly sensitive magnetic sensor both in digital and analogue operations. This magnetic sensor using the ceramic superconductor has many advantages over the conventional semiconductor magnetoresistive sensor.

Functional arrayed detector for bubble domains employing multiple three-terminal hall elements

A new principle of a functional arrayed detector for bubble domains employing multiple three-terminal Hall elements is reported with experimental results. Theories are developed, on the fundamental characteristics and requirements for the detector are discussed. When two three-terminal Hall elements are connected in parallel, an output voltage appears only when a bubble domain is present at either of the two elements, and thus an Exclusive OR operation of bubble domain logic can be performed in the process of detection. Various types of one- and two-dimensional arrayed detectors up to 100 bits were made on this principle with both InSb single crystal and vacuum deposited thin film of InSb. Maximum sensitivities of 20 and 15 mV/mA kG were obtained, giving output voltages of 2 and 3 mV for bubble domains in YFeO 3 at a bias field of 20 Oe, with vacuum deposited film and single crystal InSb detectors, respectively, with an excellent S/N ratio. Exclusive OR operation was confirmed in the performances. Applicability to the small domains in garnet is also discussed.

High Frequency Transport Properties in InSb under a Magnetic Field

Theoretical calculation has been made on high-frequency transport properties of InSb under a d.c. magnetic field, leading to the conclusion that the relative increase of microwave loss in InSb under a magnetic field, γ l , is given by γ 0 {1+ω(τ e +τ h )}, where γ 0 is the relative resistivity increase Δ ρ/ρ 0 under a d.c. magnetic field with d.c. current, and τ e and τ h are the constant relaxation times for electrons and holes respectively. Measurements were made on the microwave power loss at 34 Gc/s at room temperature under magnetic fields up to 1.5 weber/m 2 . The experimental results show an appreciable influence of ωτ on the loss even at room temperature as predicted by the theory.

Magnetic field dependence of voltage noise in Y1Ba2Cu3O7-x ceramic superconductor film

Magnetic field dependence of voltage noise in a ceramic superconductor Y1Ba2Cu3O7-x film has been investigated. We have observed a maximum of the noise at about 10 Oe for the perpendicular field to the film surface. For the parallel field to the film surface, the noise increases slightly with the increase of the field. These noise characteristics are considered due to a motion of magnetic flux in the film.

New galvanomagnetic device with directional sensitivity

A principle and characteristics of a new galvanomagnetic device, in which a Hall effect and a magnetoresistance effect in semiconductor are combined together, are described. This new device shows directional characteristics, i.e. very high sensitivity for one direction of a magnetic field and practically no sensitivity for the other direction of the field.

Liquid Phase Epitaxial Growth of Gax In1-x Sb by Vertical Dipping Method

Epitaxial growth of Gax In1-x Sb on InSb or GaSb substrate was made by using a vertical dipping-type furnace, over a whole range of x to investigate the surface morphology of the grown crystal, interface between the epitaxial layer and substrate, electrical properties and lattice constant, in connection with the type of surface, i.e. A or B, of (111) InSb substrate. The growth rate was always about 1.7 times higher on the A surface than on the B surface, irrespective of the value of x. The surface morphology of the grown epitaxial layer depends much on the type of surface of the InSb substrate, and also on the layer thickness. However, the electrical properties do not depend on the type of the surface of the substrate, and agree with the reported results. The InSb substrate was eroded to take Ga metal in it during the epitaxial growth. The reason for the erosion is explained by use of the free energy and the observed disagreements in the phase diagram are discussed in detail.

Anisotropy and Hysteresis Behavior of Galvanomagnetic Effect in Super Magneto-Resistor

The hysteresis behavior, fluctuation and their anisotropy of galvanomagnetic effect in novel magnetic sensor using bulk and film samples of ceramic superconductor Y-Ba-Cu-O have been measured. For the bulk element, the hysteresis was observed and its property was independent of the direction of magnetic field. For the film element, when the magnetic field direction was perpendicular to the element surface, the hysteresis was observed in a way similar to the bulk element, but when the magnetic field direction was parallel to the element surface, the hysteresis was eliminated to zero and fluctuation of output voltage was greatly reduced. These properties can be explained by considering the dynamics of magnetic flux trapping in the element.

Electron Velocity-Field Characteristics of GaxIn1-xSb Measured by a Microwave Heating Technique

The electron velocity-field (v–E) characteristics of GaxIn1-xSb in the composition range 0.4≤x≤0.9 are measured by a microwave heating technique at 35 GHz at room temperature, to study the transferred electron effect at high frequency. New microwave cavity perturbation tequnique is developed to measure a small signal conductance against the absorbed power in order to obtain the v–E curve. The results indicate that all samples except one of x=0.4, show negative differential mobility characteristics above the threshold field. The threshold field increases from 430 V/cm to 1200 V/cm and the negative mobility decreases with increasing x. For x=0.4, an impact ionization prevents from mesuring a negative differential conductivity. These results suggest that a useful Ga composition range of x for transferred electron devices is between 0.55 and 0.82, and that the response time of hot electrons is not much different from that in GaAs.

Continuous Coherent Microwave Oscillation from n InSb

Continuous coherent oscillation from nInSb at 77°K under transverse magnetic field is investigated experimentally. The oscillation frequency is measured in detail as a function of the magnetic field together with the threshold relation between the magnetic field and the current. Interpretation is made in terms of the helical‐mode instability both on the threshold and in the growing‐wave conditions assuming the formation of a microplasma filament.

CONTINUOUS, COHERENT OSCILLATION IN n‐InSb

Detailed measurements of the oscillation frequencies in n‐InSb at 77°K as a function of dc sample current and magnetic field are described. These show the existence of two modes of instabilities, which are in the ranges of 0.2 to 0.8 GHz and of a few to several tens of MHz, respectively.