Microscopic magnetic and high-frequency properties of a stress sensor using FeCoBSi magnetostrictive thin films

Magnetoelastic thin films are applied in remote interrogatable high-frequency devices. Integrated LC circuits operating at a frequency of 350 MHz are demonstrated. Due to the incorporation of the magnetic thin films, their inductance is sensitive to the applied external stress. A demonstrator was built, allowing a visualization of the effect of tensile and compressive strain on the device response. A comparison of the demonstrator measurement with high-frequency properties and the domain structure of the magnetoelastic layer proves an efficient integration of the magnetic material. The differences between predicted and measured device performance are related to an additional local stress distribution inside the magnetic device thus leading to an inhomogeneous stress and a locally varying magnetic anisotropy distribution. The investigations are essential for future applications of the devices as strain gauges or torque sensors. Index Terms--Domains, ferromagnetism, high frequency, permeability.