The Thickness Dependence of Soft Magnetic Properties of (FeCo)-Al Alloy Thin Films

A systematic study of the film-thickness dependence of soft magnetic properties and magnetization dynamics of Fe
₇₃
Co
₂₅
Al
₂
alloy thin films has been carried out. These films have columnar structures grown along the film normal, with the average width of the columns of about 30 nm. The saturation magnetization M
_s
is about 1550 emu/cc, which remains nearly unchanged with film thickness over a range from 10 to 120 nm. The coercivity H
_c
is found to increase with film thickness from 15 to 64 Oe over a range of 11 to about 50 nm, and then slightly decrease with further increase of thickness. The effective damping parameter α
_eff
measured by ferromagnetic resonance over a frequency range from 12 to 66 GHz is found to decrease with film thickness, becoming 0.0004 and 0.0006, for the films deposited onto fused silica and MgO (100) substrate, respectively.