Integrating the Fluxgate principle in the Spin-Valve and AMR sensor technologies

Abstract

A new kind of magneto-resistive magnetic-field sensors, called hereafter MR-Fluxgates, is being presented in this paper. The sensors employ the general Fluxgate principle together with the anisotropic magneto-resistance (AMR) effect exhibited by AMR film-resistors or the giant magneto-resistance (GMR) effect exhibited by Spin-Valve structures. The AMR film-resistors and the Spin-Valve structures can be used as Fluxgate magnetic cores when excited along their easy magnetic axis with a periodical magnetic field-waveform, generated by a miniature planar coil. In this case, the value of the resistivity (sensor signal) of the AMR film-resistors (or Spin-Valve structures) becomes a rectangular function of time, whose duty-cycle is proportional to the measured field-component. The MR-Fluxgate design allows for suppression of the repeatability error, the time- and temperature-stability errors that limit the precision of AMR and Spin-Valve sensors. Furthermore, the MR-Fluxgate design enables the simultaneous measurement of two perpendicular field-components (i.e. x-y plane), by employment of one-single AMR film-resistor (or Spin-Valve). A complete mathematical modeling of the MR-Fluxgate sensor is presented in this work. A prototype MR-Fluxgate is presented elsewhere. © 2003 Elsevier B.V. All rights reserved.