Micromagnetics of novel perpendicular media and recording for 1 Tbit/in^2 and beyond.

摘要

In this dissertation, using a 2D/3D micromagnetic modeling based on Landau-Lifshitz-Gilbert equation, three types of novel magnetic recording media and magnetic recording scheme have been studied for recording density beyond I Tbit/in2.; The adjacent track erasure performance in patterned discrete track media is studied in modeling. Considering the double layers microstructure in state-of-the-art recording media, it is found that, with mild inter-granular exchange coupling in the top layer of media, adjacent track erasure is significantly alleviated after the track is patterned. This provides an understanding to the observed track density improvement in discrete track media. The effect of wall angle at the track edge is also studied for saturation test.; A novel recording media named percolated perpendicular media (PPM), in which magnetic grains are exchange coupled with dense nanoscale nonmagnetic pinning sites, is proposed. Our simulations indicate that, with same magnetic material compositions, better thermal stability and higher recording density can be achieved in this novel media microstructure compared to conventional granular perpendicular media (GPM). Our studies also reveal that the switching processes in percolated media are domain nucleation and domain wall motions. The effects of damping constant and recording field strength in PPM are evaluated and compared to that in GPM.; A novel sub-coercivity recording scheme, named microwave assisted magnetic recording (MAMR), is introduced. Using micromagnetic modeling, the dynamic gyromotion in a single domain magnetic particle has been investigated with microwave assisting. The effects of AC field frequency and strength, as well as the damping constant and field angular dependency, are studied. With a spin torque driven oscillator, a practical head design is proposed for implementation of microwave assisted magnetic recording. Evaluations of the recording fields in MAMR are performed. The results show that both writability and recording field gradient are greatly improved in MAMR scheme compared to conventional perpendicular recording. By controlling the oscillator width, ultra-high track density can be achieved in MAMR without shrinking down the main pole dimensions. In the end, the recording performances of MAMR on media with small grain size and high anisotropy field are studied for ultra-high recording density.