Domain width effects on the magneto-dynamic response of CoFeB element arrays

Understanding the role of the magnetic domain structure on the magneto-dynamic properties of patterned magnetic thin film structures is crucial for the optimization of devices, e.g. recording heads and integrated inductors. Arrays of rectangular amorphous Co40Fe40B20 elements of micron size, a separation to width ratio of 1.5 and a thickness of 60 nm have been fabricated. Magneto-optical Kerr microscopy was used to study the domain structure. At zero field closure domain patterns are present whereas the domain width was systematically altered by varying the magnetic field history. The magneto dynamic response of different domain patterns with adjusted domain width was measured using pulsed inductive microwave magnetometry. We show that the resonance frequency is the lowest for broad closure domain structures and increases when the domain width is decreased.