Influence of strain on the high‐frequency magnetic properties of FeCoBSi thin films

Magnetostrictive amorphous FeCoBSi thin films for sensor applications have been investigated with regard to their magnetic properties dependent on strain. With special test jigs, allowing measurements in a vibrating sample magnetometer, Kerr-Effect microscope and high frequency permeameter, the magnetic dc and high frequency properties as a function of applied strain were investigated and correlated to the domain behavior. Under the condition that the applied strain stabilizes the magnetic easy axis in an orientation perpendicular to the high frequency magnetic field direction these magnetostrictive thin films can be used as cores of microinductors monitoring the strain via inductance changes. With FeCoBSi films a material quality factor of 10 and a high gauge factor (Δμ/μ 0 /Δe) of 2400 is obtained at 250 MHz.