Magnetic properties of [Fe_(65)Co_(35)-O/SiO_2]n multilayer thin films for high-frequency application

摘要

A series of [Fe_(65)Co_(35)-O/SiO_2]n multilayer thin films with different SiO_2 separate layer thicknesses (t = 0-3 nm) and fixed Fe_(65)Co_(35)-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 Fe_(65)Co_(35)-O grain size and magnetic properties can be adjusted by varying the thickness of SiO_2 layers. All films reveal an evident in-plane uniaxial magnetic anisotropy (IPUMA) when the thickness of SiO_2 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.