Determination of magnetic properties of ultrathin iron films using microwave stripline technique

Microwave microstrip line technique is utilized to determine the magnetic properties of ultrathin iron (Fe) films. Wideband tunable microwave filters are fabricated, either in integrated or flip-chip type, on ultrathin Fe films grown on GaAs substrates using molecular beam epitaxy. Taking advantage of the ferromagnetic resonance effects of the Fe films, four-fold variation of the resonance frequency is found to relate directly to the tetragonal symmetry of in-plane anisotropy. As a result, effective magnetization 4πMeff, four-fold in-plane anisotropy K1, second order term of perpendicular uniaxial anisotropy Ku⊥, and the Gilbert damping factor of the ultrathin films are derived from Landau–Lifshitz equation and transmission characteristics of the microwave filters involved.