High frequency characteristics of FeCoAlO thin films combined the effects of stress and magnetic field

The soft magnetic FeCoAlO thin films with different response at high frequency were prepared by using RF magnetron sputtering. Two different configurations of the sputtering targets were used: the Al 2 O 3 chips were placed on Fe 70 Co 30 disk either uniformly dispersed on the sputtering area (Target-A) or dispersed on the half side of the sputtering area (Target-B). It was found that, although, the films deposited from both of Target A and B possessed good soft magnetic properties and in-plane uniaxial magnetic anisotropy, they showed different behaviors at high frequency. The films deposited by using Target-A have mean permeability of 500 and a cut-off frequency ( f r ) of around 780 MHz, while the films deposited by using Target-B have mean permeability of 200 and a f r of 3.4 GHz. The higher f r of the later corresponds to the higher uniaxial anisotropic field in the films deposited by using the Target-B, which due to an extra anisotropy induced by the stress resulted from gradient of the Al-O composition. By adjusting the configuration of Target-B, the permeability & f r can be tuned to satisfy the different requirements for certain industrial applications.