Magnetic properties of [Fe₆₅Co₃₅–O/SiO₂] _n multilayer thin films for high-frequency application

Abstract

A series of [Fe₆₅Co₃₅–O/SiO₂] _n multilayer thin films with different SiO₂ separate layer thicknesses (t=0–3 nm) and fixed Fe₆₅Co₃₅–O layer thickness (5.4 nm) have been fabricated on (100) silicon and glass substrates by reactive magnetron co-sputtering. Microstructure analysis and magnetic measurement results show that Fe₆₅Co₃₅–O grain size and magnetic properties can be adjusted by varying the thickness of SiO₂ layers. All films reveal an evident in-plane uniaxial magnetic anisotropy (IPUMA) when the thickness of SiO₂ monolayer changes from t=0 to 3 nm. The hard axis coercivity (H _ch) reveals a minimum of 9 Oe at t=1 nm while the easy axis coercivity (H _ce) exhibits a minimum of 16 Oe at t=2 nm. For t=1 nm and 2 nm, the IPUMA fields (H _k) are 95 and 207 Oe, the saturation magnetizations (M _s) are 1.8 and 1.6 T, the real part of the complex permeabilities (below 3.0 GHz) are more than 217 and 104, and the ferromagnetic resonance frequencies (f _r) are 3.6 and 5.2 GHz, respectively.