Exchange-Coupled Magnetic Bilayer Media for Thermomagnetic Writing and Flux Detection

Nemoto, Hiroaki; Saga, Hideki; Sukeda, Hirofumi; Takahashi, Masahiko

doi:10.1143/jjap.38.1841

Cited by 24 publications

(8 citation statements)

References 5 publications

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“…Magnetic read-out requires optimization of the M s at the read-out temperature. Figure 5 shows the magnetic properties of a double-layer MO-type medium, adopted by Nemoto et al 7 of Hitachi to thermally-assisted writing and read out at room temperature. The magnetization of almost 300 kA/m ͑300 emu/cm 3 ͒ of the read-out layer at room temperature is convenient for magnetic read-out.…”

Section: Requirements and Improvementsmentioning

confidence: 99%

Disk recording beyond 100 Gb/in.2: Hybrid recording? (invited)

Ruigrok

Coehoorn

Cumpson

et al. 2000

Journal of Applied Physics

214

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A new method for recording above 100 Gb/in.2 is discussed. We call this method “hybrid recording,” a form of thermally-assisted recording that combines thermo-magnetic writing and magnetic reading. In order to increase the stability of the recorded information, writing is carried out at an elevated temperature on a medium with a very high coercivity at room temperature. In our proposal write and read heads with extremely narrow trackwidths are used, so the trackwidth is not determined by the optical spot size and the written bits have a rectangular shape, in contrast to the schemes proposed by others. Preliminary experiments are shown. The applicability of today’s granular and MO type media for hybrid recording is discussed. It is calculated that hybrid recording on optimized media can give an increase of the areal density of a factor 2.9 in areal density or 7 dB (2.2×) medium SNR improvement in case of Poisson noise and 11 dB (3.4×) in case of transition noise. Practically a factor of about 2 in density is more realistic, pushing limiting densities for longitudinal recording to 100–200 Gb/in.2. Typical limitations at very high densities arise from heat dissipation in the head and thermal instability of the medium. Based on simplified model calculations including realistic limitations on medium, head and leads, and today’s practical limitations on electronics, comparisons are made between read heads containing a tunnel junction magnetoresistive (TMR) element and containing a giant magnetoresistive element with sense current in the plane (CIP-GMR) or perpendicular to the plane (CPP-GMR) of the sensor films. They show that the signal-to-noise ratio of TMR sensors for areal densities above 15 Gb/in.2 is not advantageous over GMR sensors with sense current in the plane as long as the junction’s tunnel resistance is not drastically reduced to below 10 Ω μm2. The CPP-GMR heads are disadvantageous with respect to CIP-GMR heads until the highest densities, 300 Gb/in.2, considered.

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Section: Requirements and Improvementsmentioning

confidence: 99%

Disk recording beyond 100 Gb/in.2: Hybrid recording? (invited)

Ruigrok

Coehoorn

Cumpson

et al. 2000

Journal of Applied Physics

214

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“…With increasing Sm composition, it was found the M s increases without compromising a lot in H c , and M s as high as 385emu/cm 3 31 Co 69 (120nm)/Cr(180nm) films [27] . Besides the single layer MO media, exchange-coupled double layer amorphous MO media has attracted much attention [23][24][25] . The typical film structure is shown in Fig.6 been obtained in such kind of media [25] .…”

Section: Magneto-optical Amorphous Media For Hybrid Recordingmentioning

confidence: 99%

Advanced hybrid recording media

Cheng

Jin

et al. 2005

SPIE Proceedings

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Abstract:Combining the advantages of hard-disk magnetic recording and magneto-optical recording, hybrid recording is regarded as promising candidate for extremely-high density recording technology beyond Tera bits/in 2 . To obtain such high areal density, hybrid recording media are required to have high coercivity and large remanent magnetization at room temperature, the desired temperature dependence of coercivity and magnetization, as well as very short thermal response time. Currently, the researches on the hybrid recording media mainly involve the magnetic hard-disk polycrystalline recording media and the magneto-optical amorphous media. This report presents the latest progresses in the researches on these two kinds of media for hybrid recording.

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“…1, the magnetic field from the medium, incident on the GMR 0018-9464/01$10.00 © 2001 IEEE (1) where is the medium thickness, is the sensor free layer thickness, and is sensitivity function of the head, which is computed as (2) where is the perpendicular component of the head sensitivity function at each point through the depth of the media, from the top surface of the medium at to the bottom surface at . The medium thickness is .…”

Section: A Normalized Head Sensitivitymentioning

confidence: 99%

Iterative soft decoded partial response channels for hybrid magneto-optical recording

Song

Liu²,

Kumar³

et al. 2001

IEEE Trans. Magn.

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In this paper, a physical model of readback signals from a hybrid magneto-optical (MO) recording using magnetic flux detection is presented. The minimum mean-square error (MMSE) technique has been used to design generalized partial response (GPR) targets in order to facilitate the application of the trellis based channel detector. A PR target with integer coefficients is proposed as a good approximation to the GPR target. We also address the application of turbo codes and LDPC codes with iterative soft decoding structure to the hybrid magneto-optical (MO) recording channel. The effects of bloom, transition noise and giant magneto-resistive (GMR) sensor nonlinearity on the bit error rate (BER) performance are investigated both for uncoded partial response maximum likelihood (PRML) and iterative soft decoded recording channels. Our results for the hybrid recording channels indicate that turbo/LDPC codes of rate 16/17 can achieve coding gains of about 5 dB over PRML methods for a 10 5 target BER at the normalized density = 1 5. Turbo codes with iterative soft decoding are seen to be robust to transition noise.Index Terms-Bloom, generalized partial response (GPR) target, hybrid magneto-optical recording, iterative soft decoding, low density parity check (LDPC) codes, minimum mean-square error (MMSE), transition noise, turbo codes.

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Exchange-Coupled Magnetic Bilayer Media for Thermomagnetic Writing and Flux Detection

Cited by 24 publications

References 5 publications

Disk recording beyond 100 Gb/in.2: Hybrid recording? (invited)

Disk recording beyond 100 Gb/in.2: Hybrid recording? (invited)

Advanced hybrid recording media

Iterative soft decoded partial response channels for hybrid magneto-optical recording

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