Microwave generation of bubble domains in magnetic thin films

The generation of bubble domains in nonconducting magnetic thin films by strong localized microwave fields has been simulated on a computer. The excitation region was modeled as a small cylinder, driven by a uniform microwave field, within a film of infinite extent. Material characterization data were taken from Dotsch, however the cubic crystalline anisotropy contribution was omitted for simplicity. The resonant frequency, ωr(θ) for the system modeled using these data is dominated by the uniaxial crystalline anisotropy contribution, Hk(θ). Here, θ denotes the magnetization tilt angle. When circularly-polarized microwave excitation of the proper sense and of sufficient amplitude is applied, bubble generation (flipover) occurs. The system responds most strongly when the driving frequency, ω, is below the small signal resonance frequency, ωr(0), which is computed to correspond to 1.78 GHz for our modeling. We find, at 1.0 GHz, that a microwave amplitude of 110 Oe is sufficient for flipover. Data on the time required for flipover have also been obtained.