Recent Advances of Pico-Tesla Resolution Magneto-Impedance Sensor Based on Amorphous Wire CMOS IC MI Sensor

Abstract

We have developed sensitive micro magnetic sensors referred to as MI sensors based on magneto-impedance effect in amorphous wires and CMOS IC electronic circuits providing a sharp-pulse excitation. Micro sized MI-HIC chips have been in mass production of electronic compasses by Aichi Steel Corp. since 2002 for mobile phones and since 2010 for smart phones. Recently we have realized pico-Tesla (10-8 Oe) resolution for micro MI sensors making use of ultralow intrinsic magnetic noise in amorphous wires with the pulse magnetoimpedance effect. The pico-Tesla MI sensor is useful especially for bio-magnetic measurements without any magnetic shielding at room temperature. In order to avoid a risk of traffic accident due to noise reduction electric vehicles, an alert system for the pedestrians having a smart phone would be useful, if pico-Tesla MI sensor were built in the smart phones.