International Business Machines Corporation

Yoshiaki Sonobe

Manfred Ernst Schabes

Yoshihiro Ikeda

Kentaro Takano

Martin Aureliano Hassner

Dieter Klaus Weller

Barry Marshall Trager

Hoa Van Do

Bertrand Gabillard

Francesco Brianti

A Hilbert transform is used to process perpendicular magnetic recording signals from both single layer and dual layer disks to produce a complex analytic signal. This complex analytic signal is used to derive angles of magnetization, which depend on the distance between recorded magnetic transitions and consequently which can be used in error estimation. Moreover, the Hilbert transform in cooperation with an equalizer FIR optimizes transformation of the signal such that conventional longitudinal recording processing methods can subsequently be used to process the signal that is read back from the magnetic recording medium.

Perpendicular signal equalization and timing recovery using Hilbert transform

A perpendicular magnetic recording disk has an underlayer structure that causes the magnetic layer to have perpendicular magnetic anisotropy and high signal-to-noise ratio (SNR). The underlayer structure comprises a B2 type body-centered-cubic (BCC) material, such as the binary alloys NiAl, RuAl and RuTi, as an underlayer, and a Ti or TiCr alloy sublayer formed directly on the underlayer. The magnetic layer, such as a CoCrPt alloy, is deposited directly on the sublayer. The magnetic layer has perpendicular magnetic anisotropy due to the sublayer yet excellent SNR because of the smaller grain size of the sublayer material formed directly on the B2 type underlayer.

Magnetic recording disk with perpendicular magnetic recording layer and multilayered underlayer structure

A composite perpendicular magnetic recording disk has two distinct magnetic layers formed on the disk substrate, each with strong perpendicular magnetic anisotropy, that are strongly exchange coupled perpendicularly to each other across their interface. The first layer is a CoCr granular layer formed on a growth-enhancing sublayer, such as titanium, so as to have strong perpendicular magnetic anisotropy. The second layer is a continuous layer, preferably a continuous multilayer of Co/Pt or Co/Pd palladium formed on top of the granular layer. An interface layer, such as a layer of platinum or palladium, depending on whether the top multilayer is Co/Pt or Co/Pd, respectively, may be located between the two layers to enhance the growth of the continuous multilayer.

Magnetic recording disk with composite perpendicular recording layer

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Yoshiaki Sonobe