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The single-particle energy surface model is utilized to study the switching field limit and the magnetization ringing in the dynamic reversal process. A simple analysis of magnetization ringing is shown and a method to reduce magnetization ringing in dynamic switching is suggested. We show that for the applied field smaller than the grain anisotropy field, the magnetization ringing is reduced with decreasing applied field magnitude. The energy surface model also predicts that for high data rate magnetic recording, the dynamic switching field may be well below the Stoner–Wohlfarth value. The magnetic write width can be much larger than the physical write pole width in perpendicular magnetic recording systems. [ABSTRACT FROM AUTHOR]

Dynamic relaxation for nonlinear magnetization excitation is analyzed. For direct processes, such as magnon-electron scattering and two-magnon scattering, the relaxation rate is determined from the linear case simply by utilizing the magnetization oscillation frequency for nonlinear excitation. For an indirect process, such as slow-relaxing impurities, the analysis gives an additional relaxation term proportional to the excitation level. In all cases the effective magnetization damping is increased compared to Landau-Lifshitz-Gilbert damping. [ABSTRACT FROM AUTHOR]

Track edge effects in tilted and conventional perpendicular recording are analyzed. The write fields are calculated utilizing a three dimensional micromagnetic simulation that includes both the write pole and the soft underlayer. The dynamic reversal time and thermal stability of the recording layer are analyzed using a recent model involving mode analysis and the optimal collective reversal barrier. For conventional perpendicular recording, the effect of the write field angle at the track edge is to lower the medium energy barrier, which increases the guard-band width. For tilted perpendicular recording, the guard band is decreased due to an energy barrier increase caused by the write field angle. [ABSTRACT FROM AUTHOR]

Poisson's equation is solved exactly to obtain the medium demagnetization field for both a single pole head and a single pole with a trailing shield (shielded single pole) head designs in perpendicular recording. To write an isolated transition, for the semi-infinite single pole head, head imaging can be neglected when calculating the demagnetization field. To the semi-infinite shielded single pole head, when the pole separation is reduced, perfect imaging from both the head and the soft magnetic underlayer is a good approximation. [ABSTRACT FROM AUTHOR]

Presents a three-dimensional micromagnetic modeling of shielded giant magnetoresistive heads with a spin-valve sensor. Formulation scheme of the model; Shielded spin-valve head response.

Examines the computation of magnetostatic fields in magnetic recording problems using Bramble-Pasciak-Xu multilevel preconditioners. Information on the magnetization of media in micromagnetic problems; Development of magnetostatic field algorithms for micromagnetic simulations; Advantages of using multigrid methods for the calculation of magnetostatic fields.

It is conceivable that early generations of patterned media will utilize read heads whose dimensions are several times larger than an ‘island’ of magnetization. For such a scenario, we propose a ‘multiple islands per read head’ model where the output from the read head is a function of the magnetization from several independently written tracks of islands. In particular, we focus on a ‘3 islands per read head’ model where the output from the read head is a function of the magnetization from three independently written tracks of islands. The readback signal is determined from a finite track-width magnetoresistive (MR) head model using reciprocity calculations, and two noise sources—island position jitter and AWGN electronics noise—are considered. By sampling the noisy signal at intervals corresponding to the down-track island separation, we obtain a discrete-time readback channel model whose performance is obtained under maximum-likelihood sequence detection. [ABSTRACT FROM AUTHOR]

Noise caused by thermal magnetization fluctuations in giant magnetoresistive sensors, mainly in the free layer, limits the achievable signal-to-noise ratio and thus the density of magnetic recording systems. Here, we describe a quasi-analytical method to study this noise. First, by discretizing the free Layer into sufficiently small rectangular cells, an equilibrium state of the free layer is obtained using a quasi-static energy minimization technique. A linear tensor relation between the magnetization spectra and the thermal fluctuations is found for the two approaches: 1) Landau-Lifshitz-Gilbert-Brown and 2) collective spin wave excitation. In the former, damping and thermal fields are added to each cell and then a Fourier transform is taken to obtain the spectra. For the eigenmode approach, the lossless dynamic equations are diagonalized, yielding the system's intrinsic eigenmodes. Then damping and thermal fluctuations are added to each eigenmode, independently. The sensor playback noise power spectrum density, a measurable quantity, is calculated by sununing up the contributions from each eigenmode or cell magnetization. This computationally light treatment yields a clear physical picture of the phenomenon, relating damping, thermal fluctuation, and noise. We describe each step of the calculation procedure in detail and give examples. [ABSTRACT FROM AUTHOR]

Provides information on a study which examined a system of magnetic grains with resonance interactions. Criterion of resonance interaction; Indirect interaction of grains via antiferromagnetic substrate; Conclusion.

Micromagnetic simulations have been performed to compare longitudinal thin film media with and without a grain size distribution. Hysteresis loops and dibit recording are evaluated for various exchange interactions. The results show that the grain size distribution reduces effects of both intergranular exchange and magnetostatic interactions. [ABSTRACT FROM PUBLISHER]

The energy barrier to be overcome for thermal reversal, the reversal mode and the effective particle volume involved are determined by the saddle points of the energy surface. We investigate the influence of field misorientation, exchange-coupling and magnetostatic interaction for a 2:1 aspect ratio particle discretized into two subunits. typically, increasing the field angle from 0° to 45° enhances the effective volume in both cases by more than 20%. [ABSTRACT FROM AUTHOR]

Discusses a study which examined thermal energy barrier distributions in longitudinal recording performing micromagnetic simulations. Description of the micromagnetic simulation model; Overview of the thermal decay model; Results; Conclusion.

Focuses on a study which examined switching speed in perpendicular recording media from micromagnetic simulations, by applying a uniform reversal field to an array of magnetic grains. Description of the model; Effects of applied field strength; Effect of damping constant; Effect of exchange coupling.

Presents a study which analyzed measurements on elongated particles in magnetic tape using a model of reversal field versus pulse time. Description of the model; Results; Discussion; Conclusion.