Bridge circuit magnetic field sensor having spin valve magnetoresistive elements formed on common substrate

A bridge circuit magnetic field sensor for generating an output voltage in response to an external magnetic field, the sensor comprising:

• a generally planar substrate;
• first, second, third and fourth generally rectangularly shaped spin valve elements having inherent widths and lengths and formed on the substrate with their lengths oriented generally parallel, each of the spin valve elements comprising (a) a free ferromagnetic layer having a preferred axis of magnetization oriented generally parallel to the length of the spin valve element in the absence of an applied magnetic field, (b) a nonmagnetic spacer layer adjacent to the free ferromagnetic layer, (c) a pinned ferromagnetic layer adjacent to the spacer layer, and (d) an exchange bias layer of antiferromagnetic material adjacent to and in contact with the pinned ferromagnetic layer for pinning the magnetization of the pinned layer in a direction generally parallel to the width of the spin valve element, the direction of magnetization of the pinned layers in the first and fourth spin valve elements being substantially parallel to one another and substantially antiparallel to the direction of magnetization of the other two pinned layers;
• a first electrically conductive layer formed on the substrate and interconnecting the first and second spin valve elements, the second and fourth spin valve elements, the fourth and third spin valve elements and and the third and first spin valve elements, the first conductive layer including terminal leads located between adjacent spin valve elements, the terminal leads between the first and second spin valve elements and between the third and fourth spin valve elements being for the application of sensor input power and the terminal leads between the first and third spin valve elements and between the second and fourth spin valve elements being for the sensor output voltage;
• a second electrically conductive layer formed on the substrate and aligned with the spin valve elements for conduction of a fixing current to orient the direction of magnetization of the pinned layers of the spin valve elements during fabrication of the sensor;
• an insulating layer between the spin valve elements and the second electrically conductive layer to electrically insulate the spin valve elements from the second electrically conductive layer;
• and
• a power source connected to the input terminal leads;
• whereby the output voltage provides a measure of the external magnetic field component substantially in the plane of the substrate and in a direction substantially perpendicular to the lengths of the spin valve elements.