Performance modelling of micromachined sensor membranes coated with piezomagnetic material

In this paper we model the performance of piezomagnetically coated membranes for contactless sensor applications. When a mechanical stress (pressure) is applied to a membrane the piezomagnetic characteristic of the coating causes a change in its magnetic permeability. The membrane can then be coupled with a micromachined coil to form a cored inductor, the inductance of which will change as the permeability of the coating varies with the applied stress (piezomagnetic effect). The applied stress and magnetostriction of the coating also cause the distance between the coil and the membrane to vary, thus altering the inductance (geometric effect). We decouple these combined effects and compare their magnitudes. The piezomagnetic effect is found to be approximately two orders of magnitude greater than the geometric effect. The results demonstrate the feasibility of piezomagnetically coated membranes for remote sensing and show significant promise in the development of second-generation device concepts.