Integrated magnetic sensor using spin tunneling effect

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Magnetic sensor devices using a giant magnetoresistance effect and a spin tunneling effect were developed and their sensing characteristics were investigated. In order to prepare sensor devices, Co/Cu multilayers and Ta/CoFeB/Cu/CoFe/MnR/Al spin valve films were patterned to strip lines by means of photolithography, which had a shape of 30μm width and 200μm length. Spin tunneling devices with 10×10μm^2〜30×30μm^2 junction, whose structure was Ta/CoFe/MnIr/CoFeB/Al_2O_3/CoFeB/Ta made by 8 sources magnetron sputtering system, were prepared by photolithography. Electronic sensor circuits with a frequency sift type and a voltage shift type, were developed for utilizing prepared magnetic sensor devices. The sensor devices were mount in center of Helmholtz coils, which generate a alternative magnetic field of 1 kHz and out put signal from the sensor circuit was observed by a synchroscope. When the external magnetic field of 1 kHz was applied in perpendicular to easy axis of the free layer of the spin valve, an out put voltage of 70 mV was obtained for 10 Oe external field and a sensitivity of 0.2 Oe was achieved. When the external field was applied in parallel to the easy axis, a larger change of out put voltage was observed compared to perpendicular case.