Modeling of Magnetization Distribution Near Shaped Boundary of Garnet Film Core in Fluxgate Magnetometer

Micromagnetic modeling of magnetization in-plane distribution near shaped boundary of garnet film was made to analyze the possibility to prevent chaotic formation of magnetic flux distortions in a fluxgate disc-like core excited by rotating magnetic field. Calculations made in the limit of zero anisotropy for sinusoidal, rectangular, and cogged (with right angle) boundaries show regular macroscopic vortex formation and annihilation in opposite phases of external magnetic field inside every apex of garnet film shaped boundary. Vortices are formed due to magnetostatic conservation of magnetization initial local direction along smooth or straight boundaries of the film during the whole period of rotation. Vortices near smooth curved boundary exhibit a stability range in the external field that exceeds that near rectangular and cogged shapes by an order of magnitude. Transformations of vortex states and low field saturation near broken line boundary are explained by peculiarities of exchange energy caused by mutually perpendicular spin orientations along adjacent straight sides of right angles. Calculation results show the way for control of magnetization distribution distortions in fluxgate garnet disc core by film boundary shape.