Search

Coupled granular/continuous (CGC) perpendicular media with two different continuous layers, a Co/Pd multilayer and a CoCrPtB cap layer, were compared. It was confirmed that both thickness optimized layers functioned well as exchange coupled continuous layers. A Landau-Lifshitz-Gilbert simulation was performed for various grain boundary thicknesses, and the signal-to-noise ratio improvement predicted by the simulation was in good agreement with experiments. The CGC structure was susceptible to side erasure on account of its Stoner-Wohlfarth type magnetic switching, and the recording performance was dominated by the granular layer. Controlling this behavior would enable further improvement in recording density. The benefits of discrete-track media with the CGC structure are discussed. We found that ion irradiation of the CGC media could be effective to create soft magnetic regions in between recorded tracks, which act as guard bands, improving the recording performance. Index Terms--Discrete-track medium, exchange coupling, soft guard band, track edge noise.

The recording physics of bit-patterned media is studied for areal densities of around 2 Tbits/[inch.sup.2]. A model of the writing process, based on the head field gradient and switching field distribution, including various interference fields, is presented to extract the write-head and media parameters which are necessary to attain a wider write margin. Write head field distributions, calculated by the finite-element method, are presented for various head pole structures with side- and trailing-shields to improve head field gradient. Optimization of the pole configuration increased the gradient to over 500 Oe/nm for a head-to-soft magnetic under layer (SUL) spacing of 14 nm. Using the head field distribution, a recording performance analysis by micromagnetic simulation indicated that the write margin was improved. Position and size dispersions of the dots deteriorated the signal-to-noise ratio (SNR) and increased adjacent track erasure (ATE). Index Terms--Bit-patterned media, head field gradient, Landau-Lifshitz-Gilbert (LLG) simulation, perpendicular magnetic recording, single-pole head, switching field distribution.

FEM-boundary integral method micromagnetic software was used to analyze the recording field response of an indented magnetic head to high frequency recording currents (1-4 GHz). Next, micromagnetic simulations of heat-assisted magnetic recording were performed and the signal-tonoise ratio (SNR) calculated at high frequencies. With a soft magnetic underlayer, the head field was large enough and gave higher SNRs. The large head field strength at low frequency did not cause any deterioration of the SNR. [ABSTRACT FROM AUTHOR]

Jitter noise reduction can be achieved by controlling the position of magnetic grains, but write synchronization is needed to take advantage of the potential reduction. A periodic read-back response can be obtained from DC-erased bits, which is composed of rows of grains. In this paper, the feasibility of creating a clock signal for write synchronization using this periodicity of the readback response is investigated. As a result, it was confirmed that a clock signal can be created by using the precise periodicity of the read-back response. [ABSTRACT FROM AUTHOR]

In bit patterned media (BPM), a magnetic data storage medium is patterned into nanoscale magnetic islands each representing one binary digit (bit). The recording performance of BPM depends upon the variability of island position, geometry, and magnetic characteristics. To understand the impact of the distributions of these parameters on the performance of BPM a detailed statistical model of write-errors has been developed. The islands can either be single layer or two-layer exchange coupled composite (ECC) structures. The modeling of ECC islands was made possible by the development of a 2-spin model to calculate switching field, coercivity, and energy barrier as a function of applied field which enables medium design to be optimized for a non-uniform write head field. The statistical model predicts coercivities and error rates in good agreement with a micromagnetic model but at significantly lower implementation and computational cost and shows good agreement with experimental data from drag-test experiments at 500 Gbit/in2. The model enables the position tolerance of the write head to be determined from the magnetic characteristics of the write head and the storage medium and it is therefore a valuable system design tool. [ABSTRACT FROM AUTHOR]

Head and medium designs to support areal densities of 400 Gb/in² were investigated using micromagnetic modeling. The use of side shields allows the track pitch to be reduced, but only by about 10 nm. Reducing the main pole width also permits higher track densities, but the erase band width does not reduce significantly with the pole width reduction. In addition, the erase band width increases at higher linear densities and forms an increasing fraction of the total track width. [ABSTRACT FROM AUTHOR]

A single-pole-type head design for 400 Gb/in² based on finite-element method (FEM) simulations is presented. The conditions required to generate a sufficient field for this areal density are shown. To reach this density various media were considered and written track widths, erase bands, signal-to-noise ratios, and written bit patterns were derived from Laudau-Lifshitz-Gilbert (LLG) simulations. [ABSTRACT FROM AUTHOR]

Head and medium designs to support areal densities of 400 Gb/in² were investigated using micromagnetic modeling. The use of side shields allows the track pitch to be reduced, but only by about 10 nm. Reducing the main pole width also permits higher track densities, but the erase band width does not reduce significantly with the pole width reduction. In addition, the erase band width increases at higher linear densities and forms an increasing fraction of the total track width. [ABSTRACT FROM AUTHOR]