Magnetic field sensor

摘要

A magnetic field sensor has a magnetoresistive rod having a stack of stacked layers that include a pinned layer having a fixed magnetization direction almost perpendicular to a longitudinal direction, a free layer comprising a magnetostrictive material having a coefficient of magnetostriction greater than 20 ppm to 25° C. and a longitudinal axis of easiest magnetization, the magnetization changing when the free layer is exposed to a magnetic field, a non-magnetic spacer layer interposed between the free and pinned layers to form a tunnel junction or spin valve, and a stress-generating layer for exerting uniaxial stress essentially such that a product of stress and magnetostriction coefficient is greater than 500 ppm·MPa at 25° C. The rod's length is at least ten times its greatest width.

主权项

1. An apparatus comprising a magnetic field sensor, said magnetic field sensor comprising a magnetoresistive rod comprising a stack having stacked layers, said stacked layers comprising a pinned layer having a fixed magnetization direction that is within ten degrees of being perpendicular to a longitudinal direction, a free layer comprising a magnetostrictive material having a coefficient of magnetostriction, the absolute value of which is greater than 20 ppm to 25° C. and having an axis of easiest magnetization that is parallel to said longitudinal direction, said free layer having a magnetization that changes when said free layer is subjected to a magnetic field to be measured, a non-magnetic spacer layer interposed between said free layer and said pinned layer to form one of a tunnel junction and a spin valve, and a stress-generating layer capable of exerting a uniaxial mechanical stress in a direction that is within ten degrees of being parallel to said longitudinal direction such that a product of said mechanical stress and said coefficient of magnetostriction is positive and greater than 500 ppm·MPa at 25° C., said magnetoresistive rod having a length in a longitudinal direction thereof and a greatest width in a transverse direction perpendicular to said longitudinal direction and parallel to said stacked layers, said length being at least ten times greater than said greatest width.