Kazuhiko Kuroki

GIANT MAGNETORESISTANCE EFFECT IN MULTILAYERED WIRE ARRAYS

Three wire arrays, each comprised of a different type of giant magnetoresistive (GMR) multilayer, were fabricated by high‐resolution electron‐beam lithography and lift‐off techniques. With a GMR multilayer of the biquadratic‐coupling type, a magnetic field applied parallel to the wires produced a larger MR change and higher response than in the corresponding unpatterned multilayered film; however, the wire structures worsened the MR characteristics of two other types of GMR multilayers.

Origin of giant magnetoresistance effect in granular thin films

Though the demagnetization process of granular Co‐Ag films became steep by adding permalloy layer, slow saturation in the magnetoresistance (MR) curves was maintained. In addition, the MR characteristics of granular Fe‐Ag films prepared under a magnetic field, in which strong magnetic anisotropy was induced, were isotropic. The disagreement between the MR and magnetic characteristics implies that ferromagnetic granules are not responsible for the giant MR (GMR) effect. The MR ratio of the granular Fe‐Ag films considerably increased at thicknesses less than 20 nm. In such ultrathin films, the features of the MR curves corresponded well with those of the magnetization curves with slow saturation and no hysteresis. These results suggest that the GMR effect in the granular systems is attributable to superparamagnetism.

Characteristics of a liquid crystal IR chopper for pyroelectric IR sensors

Abstract We have developed an IR chopper utilizing the electro-optical effect of liquid crystals for pyroelectric sensors. This IR chopper primarily consists of liquid crystals and Si substrates with wire-grid polarizers. We have investigated theoretically the relationship between the characteristics of this IR chopper and its structure. It is confirmed that the theoretical calculations of the IR modulation degree are in approximate agreement with the experimental results. Under the condition that the IR radiation is emitted from a blackbody whose surface temperature is 150 °C, a degree of modulation of 7.4% is obtained.

Modulation-type pyroelectric infrared detector and its application

Abstract We have developed a new type of pyroelectric infrared (IR) detector that contains a sensing part and a solid-state chopper with two bimorph vibrators and two slit plates in the same package. This detector (M-type IR detector) features high reliability, small volume and low electric-power consumption compared with conventional pyroelectric IR detectors using a rotating chopper. In addition, two applications using an M-type IR detector have been investigated. One application is a new type of gas sensor, and the other is non-contact temperature measurement. For the gas sensor, the measurement accuracy is ±0.12% over a 0–20% gas concentration range. The non-contact temperature measurement system is used in a permanent-wave machine. In this system, the temperature of the hair can be accurately measured and automatically controlled. The accuracy of measurement is ±0.15°C over the temperature range 34–64°C.