Micromagnetics of Ferromagnetic Nano-Devices Using the Fast Fourier Transform Method

Micromagnetic simulations are widely utilized to simulate magnetic properties of magnetic materials, performance of magnetic devices, and read/write processes in recording systems. In hard disk drives, the minimum size of devices is now scaled down to the nanometer region; therefore, micromagnetics should be accurate enough to include the edge effects in these ferromagnetic nano-devices. In this work, we consider devices with flat structures. The analytical forms of demagnetizing matrices for intra-cell and inter-cell interactions are calculated for cubic and right-angle triangular prism cells respectively, which enables accurate magnetostatic interaction calculation using fast Fourier transform (FFT) method in thin film devices with arbitrary geometry. Besides, the parallel computational method is included to speed up the programs. Two examples about the switching characteristics of ferromagnetic devices are given in this paper to evaluate the accuracy of the improved FFT methods: one is a hard magnetic nano-dot; the other is a write pole tip for perpendicular recording.