Eric Meloche

Impact of Anisotropic Exchange on M-H Loops: Application to ECC Media

Micromagnetic simulation results on Co-based recording media are presented which examine the impact of a modified near-neighbor exchange interaction between grains of the form <i>J</i> ^z (M_i ^z M_j ^z), reflecting the hexagonal crystal symmetry. Both out-of-plane and in-plane M-H loops are calculated, with an emphasis on a model fit to data reported by Wang . [<i>IEEE Trans. Magn</i>, vol. 43, p. 682 (2007)] on exchange coupled composite perpendicular media. The principle effect of <i>J</i> ^z is to increase the coercivity and slope of both hard and soft layers. Improved agreement with experimental data for the in-plane loops is achieved by assuming a substantial value for <i>J</i> ^z . Possibilities for measurement of J^z through spin-wave excitations are discussed. Thermal fluctuation effects are also examined through simulations of the magnetization vs temperature.

Dynamic Field Gradient and Erasure After Write for High Data Rate Recording

Extensive micromagnetic simulations are performed to investigate the impact of the current overshoot amplitude (OSA) on the writer dynamics. The field risetime, dynamic gradient, bubble width, as well as erasure risk due to large stray fields in the neighbouring tracks during the switching are all shown to be very sensitive to the OSA. Numerical results show that increasing OSA can sharply improve the field risetime. However, it also leads to a larger write bubble expansion during switching which could result in a wider track width and reduce track per inch (TPI) capability. The risk of side track erasure for different overshoot conditions are evaluated and also tend to increase with higher OSA. Futhermore, results for remnant fields in the media produced by the writer are shown to be extremely sensitive to the choice of damping parameter used in the simulations.

Study of Trailing Edge Shield Magnetic Properties for Writer Performance Improvement for Perpendicular Magnetic Recording

Micromagnetic modeling is used to evaluate the effect of trailing edge shield (TES) magnetic properties on the dynamic performance of a writer used in perpendicular magnetic recording with wrapped around shield at air bearing surface. The gradient of the field increased with the increase in the TES saturation flux density and thickness; however the writer bubble width and field decreased as more flux turned toward the TES. The improvement of gradient can be vital for recording as the field can be traded-off until its just above the media switching field helping form sharp transitions between bits and reduce the bit-error-rate. The reduction in the bubble width enables higher track density. Additionally, the manipulation of the anisotropy in TES can help increase the gradient further, promoted by easier flux flow.