Patent ID: 8164331

Claim:
A magnetic field measurement method, comprising: a step of preparing a magnetic sensor which comprises: a magneto-resistive effect element which has a stacked body obtained by stacking, in a stacking direction, a magnetization-free layer, a nonmagnetic layer and a magnetization fixed layer so that the nonmagnetic layer is positioned between the magnetization-free layer and the magnetization fixed layer, the magnetization-free layer having a longitudinal direction that is perpendicular to the stacking direction; and magnetic field application means for generating a magnetic field when being supplied with a current, wherein the magnetization fixed layer has a magnetization direction that is fixed in a direction which forms an angle equal to or less than 45 degrees to the longitudinal direction of the magnetization-free layer when viewed from the stacking direction, and the magnetic field generated by the magnetic field application means forms within the magnetization-free layer an angle equal to or less than 45 degrees to the longitudinal direction of the magnetization-free layer when viewed from the stacking direction; a magnetic field application step of applying a magnetic field in a first direction for a predetermined time to the magnetization-free layer by the magnetic field application means so that magnetization of the magnetization-free layer is saturated, and magnetizing the magnetization-free layer in the first direction in the longitudinal direction thereof; a magnetic field measurement step of measuring a strength of an external magnetic field by applying the external magnetic field to the magnetization-free layer in a second direction in the longitudinal direction thereof, after an end of the magnetic field application step, the first direction and the second direction being opposite to each other, wherein a characteristic of a resistance value of the magneto-resistive effect element versus the external magnetic field has a region where the resistance value of the magneto-resistive effect element is proportional to the external magnetic field, and the magnetic field application step is performed to cause the magnetization of the magnetization-free layer to be saturated out of said region.