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We have calculated the electronic structures of FePt and Fe0.9375Mn0.0625Pt using first principle calculations based on density functional theory within the local-spin-density approximation (LSDA). The Curie temperature ( Tc) was calculated by a simple model based on the mean field approximation. A supercell structure, containing eight unit cells, was used to calculate the density of states. The saturation magnetization ( Ms) and magnetocrystalline anisotropy constant ( K ) at 0 K, and T_{c} for Fe0.9375Mn0.0625Pt were calculated to be 942 emu/cm3, 8.24 \times 10^{6} J/ \textm^3 , and 590 K, respectively. The temperature-dependent M(T) and K(T) of Fe0.9375Mn0.0625Pt were calculated using the Brillouin function and Callen–Callen experimental relation, respectively, to obtain an M_{s} and a K of 822 emu/cm3 and 6.29 \times 10^6 J/ \textm^3 at 300 K, respectively. These values meet the required Ms and $K$ of 800 emu/cm3 and 5.00 \times 10^{6} J/ \text{m}^{3} for achieving 4 Tb/in2 heat-assisted magnetic recording media (HAMR). [ABSTRACT FROM PUBLISHER]

Optimization of magnetic read widths (MRWs) and reader positions in two-dimensional magnetic recording (TDMR) is explored in order to maximize an areal density (AD) gain over shingled magnetic recording (SMR). The optimization is based on micromagnetic waveforms from 511-bit maximal-length pseudorandom binary sequence (PRBS) patterns. The identical MRWs for two readers are initially considered and the best reader offset is found in order to achieve the largest AD gain. Given the best reader offset, the MRWs for the two readers are changed to further enhance the AD gain. A software channel is utilized to identify the major contribution of the TDMR AD gain. [ABSTRACT FROM AUTHOR]

Drive-level pattern-dependent bit error rate (BER) and signal-to-noise ratio (SNR) degradation during thermal decay were studied. A 511 bit pseudorandom binary sequence was used to help reveal the fundamental relationship between degradation trends of SNR and BER. Degradation profiles of both SNR and BER within specific patterns were plotted and analyzed. In the short-term thermal decay, SNR mostly decayed at the nontransition part, while BER mostly decayed at the transition part. It was found that transition BER degradation was caused by the degradation of nontransition SNR, while nontransition bits hardly have any error until nontransition SNR degradation reached certain levels. It was difficult to observe nontransition BER degradation in thermal stability experiments, which were normally limited by time. Simulation is necessary to assist the prediction of thermal decay performance. [ABSTRACT FROM AUTHOR]

In this paper, we present a technique of noise analysis for perpendicular and shingled magnetic recording that is variance centric, i.e., with analysis focused on noise power. Measured noise from a home track viewpoint is decomposed into electronic noise, transition noise, nontransition noise, and inter-track interference components. The separation of media noise into transition and nontransition noise components is accomplished by a variance deconvolution technique. Experimental noise analysis is shown for cases of track squeeze, adjacent track erasure, and read head offset. Potential capacity gains are also assessed for the case of electronic noise improvement. [ABSTRACT FROM PUBLISHER]

In this paper, a general energy expression is developed for a cluster of multilayer exchange spring media grains. We expand the rotation of the magnetization vectors to second order in elements of an exponential unitary transformation. The first and second derivatives of the energy are determined and a damped optimization procedure is used to efficiently locate minima and transition states on the potential energy surface. In this method, the interaction of neighboring grains is taken into account and thus the effect of inter-granular exchange on the energy barrier is explicitly taken into consideration. Thus, cluster formation is seen as coherent switching of a group of grains and can be studied as a function of anisotropy and exchange distributions in the media. The lowest energy barrier for a grain or cluster is then used to construct a rate constant. We then determine rate constants for an ensemble of interacting grains from which M-H loops and magnetization decay are simulated as a function of an applied field. Both kinetic Monte Carlo and direct integration of the rate equations are used to study the kinetics of these systems. We find that thermal decay rates have better correlation with energy barriers than with nucleation fields. [ABSTRACT FROM PUBLISHER]

We have experimentally and analytically studied the writeability and recording characteristics of perpendicular magnetic recording media in which the anisotropy (Ku) of the granular oxides and the magnetization (Ms) and lateral exchange coupling (Aex) of the cap layer were varied. The analytical results are obtained with a 9-spin model, which consists of 3 grains with 3 layers each, representing dual oxide media with a capping layer. The 9-spin model estimates bit error rate (BER) using an error-pattern-correcting code (EPCC) based iterative channel model. The experimental results qualitatively agree well with the analytical results of the 9-spin model. High Ku gradient oxides and high Ms cap layer improve writeability and BER, whereas high Aex in the cap layer degrades switching field distribution and off-track capability. Media switching field and switching field distribution strongly depend on spatial distribution of the external field. Both experimental and analytical results indicate that an appropriate design of Ku graded media with an optimum cap layer can effectively reduce jitter and switching field distribution for given head fields, resulting in higher recording density. [ABSTRACT FROM AUTHOR]

A systematic investigation of the switching behavior and writeability characteristics of perpendicular magnetic oxide media was performed by varying the number of oxide layers as well as the anisotropy Ku gradient in multilayered oxides. The media switching behavior highly depends on the magnetic volume of laterally exchange-coupled cap layer as well as the vertical exchange coupling between oxide and cap layers. The media switching field is significantly reduced with incoherent switching mode. The media writeability is further enhanced by employing the multilayered oxides whose anisotropy values vary. Higher Ku graded oxide media exhibits improved resolution, sharper transition, and higher signal-to-noise ratio. An analytical 9-spin model is used to study the impact of anisotropy grading, intergranular and interlayer exchange coupling on writeability and noise performance. The 9-spin model is found to qualitatively agree with the experimental results. Both model and experiment indicate that optimal tuning of the media anisotropy and exchange to the head design is critical in attaining good recording performance. [ABSTRACT FROM AUTHOR]