MAGNETORESISTIVE SENSOR FOR WEAK MAGNETIC-FIELDS

A new excitation technique is described for the measurement of weak ma gnetic fields (<0.01 Oe). The resistance variation of a magnetoresisti ve element due to an oscillating excitation field is converted into a voltage proportional to the environmental field. The excitation field amplitude is set large enough to saturate the magnetization during eac h half-cycle, greatly reducing hysteresis effects in the output signal . Both anisotropic magnetoresistance (AMR) and giant magnetoresistance (GMR) structures have been used to measure fields with sufficient acc uracy for compass applications. Such devices could be made with extrem ely small dimensions and power requirements. (C) 1997 American Institu te of Physics.