High sensitivity spin-valve strain sensor

A technique for detecting strain has been demonstrated based on a spin-valve sensor. The 400 Å thick sensor has been integrated onto an atomic force microscope cantilever. An applied strain caused by bending of the cantilever changes the orientation of the free-layer magnetization due to magnetostriction. This in turn results in a change in the electrical resistance because of the giant magnetoresistance effect. With the proper magnetic bias, a base-line strain sensitivity of 10-10/Hz1/2 has been achieved. The corresponding gauge factor of 150 is roughly 1.6× that of similar silicon piezoresistive cantilevers. In the future, one might be able to enhance the sensitivity by another factor of 3-5. © 1998 American Institute of Physics.