Enhancement of Microwave Properties of FeCoN Films on Mica Substrates by Control of SiO2 Underlayer Thickness

A thin SiO
₂
underlayer has been found to be effective to enhance the microwave properties of FeCoN films on mica substrates. In this study, the effect of SiO
₂
thickness on static and dynamic magnetic properties was studied. A 160 nm FeCoN film directly deposited on a mica substrate exhibited in-plane isotropy, accompanied by a large coercivity of 70 Oe. By inserting a thin SiO
₂
as the underlayer, the anisotropy and coercivity were dramatically changed. When the thickness of SiO
₂
was 40nm, the film had well-defined in-plane anisotropy, and the coercivity greatly decreased to less than 3Oe. Correspondingly, excellent microwave properties were obtained with a strong magnetic resonance at 2.8GHz. However, both the static and dynamic magnetic properties declined rapidly with the further increase in the thickness of SiO
₂
, which is related to the large damping effect due to the increased surface roughness and residual stress of the SiO
₂
layer.