High sensitivity spin-valve strain sensor

A technique for detecting strain has been demonstrated based on a spin-valve sensor. The 400 Angstrom 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)/Hz(1/2) has been achieved. The corresponding gauge factor of 150 is roughly 1.6x that of similar silicon piezoresistive cantilevers. In the future, one might be able to enhance the sensitivity by another factor of 3-5. (C) 1998 American Institute of Physics.