Comparison of media properties between hard/soft stacked composite and capping layer perpendicular recording media

Jung, Hongsik; Vélu, E.; Malhotra, S.S.; Bertero, G.; Kwon, U.

doi:10.1016/j.jmmm.2008.08.077

Journal of Magnetism and Magnetic Materials

2008

DOI: 10.1016/j.jmmm.2008.08.077

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Comparison of media properties between hard/soft stacked composite and capping layer perpendicular recording media

Hongsik Jung

E. Vélu

S.S. Malhotra

et al.

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Cited by 7 publications

(8 citation statements)

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“…These simulation results are also supported by the previous reported results. 11 From the simulated results, the decrease in H c with increasing t soft is anticipated when K u soft reduces by Ͼ27%. However, the simulation results do not show the decreases in H c even for the soft layer with K u soft = 2.9ϫ 10 6 ergs/ cm 3 .…”

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confidence: 88%

“…H/S media with the Pt 3% soft layer having H k ϳ 5 kOe and saturation magnetization ͑M s ͒ ϳ 500 emu/ cm 3 improved SNR and MWW compared to CL media but it did not improved media writability indicated by reverse OW ͑OW2͒ and dc-erase SNR ͑SNR dc ͒. 11 Interestingly, CL media showed the peak of coercivity ͑H c ͒ with increasing t cap while H/S media exhibited constant H c or the continuous decrease in H c ͑Fig. 1͒.…”

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confidence: 97%

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Effect of magnetic softness in a soft layer on media properties of hard/soft stacked composite perpendicular media

Jung

Malhotra

Acharya

et al. 2009

Journal of Applied Physics

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Adding Pt into CoCr-oxide alloy for controlling magnetic softness in a soft layer on hard/soft ͑H/S͒ stacked composite media significantly affects magnetic properties and microstructure. H c values for capping layer ͑CL͒ media with a relatively high-H k soft layer initially increase with increasing t cap . However, H c values are relatively constant for H/S media with Pt 3% and 10% soft layers and reduced for the media with a CoTaZr-SiO 2 soft layer having in-plane H k . The simulation results explain these experimental H c trends by the compensation effect between the decrease in average K u due to the use of less-K u soft layer and the increases in volume with increasing t soft . Reduction in H c with increasing t soft is anticipated when K u in a soft layer reduces by Ͼ27%. As the Pt content in a soft layer increases from 3% to 18%, higher H c and H n but lower H s are observed. Plan-view transmission electron microscopy images for the medium with Pt 18% soft layer show no subgrains and thinner grain boundary width and explain the significant increase in lateral A ex . Thus, the Pt content in a soft layer needs to be optimized. Compared to CL media, H/S composite media with the Pt 5% and 8% soft layers improve both SNR me and media writability.Advanced hard/soft ͑H/S͒ composite media structures with a concept of dynamic magnetic switching are currently in development for further improvement of areal density. A soft layer exchange coupled with the hard layer provides shallow angular dependence of remanent coercivity ͑H cr ͒, providing the improvement of media writability and signalto-noise ratio ͑SNR͒. Incoherent switching behavior via a soft layer occurs in exchange-coupled composite ͑ECC͒, 1 exchange spring, 2 and anisotropy graded 3 media while coherent switching behavior is anticipated in H/S media with a thin soft layer. 4 Compared to conventional capping layer ͑CL͒ media with a high magnetic anisotropy field ͑H k ͒-soft layer, ECC media can improve media writability, SNR, and biterror-rate but head dependence effect needs to be considered. The simulation results 5 showed the best performance in ECC media with the parameters of H k = 6 kOe, intergranular exchange coupling constant ͑A ex ͒ =1ϫ 10 −7 erg/ cm in a soft layer, and interlayer exchange coupling strength ͑J in ͒ between soft and hard layers= 2 ergs/ cm 2 . Tanahashi et al. 6 recently demonstrated that even H/S dual media with graded properties achieve high areal density of 612 Gbytes/ in. 2 .Head field gradient and field strength typically trade off in trailing shielded-pole ͑TS͒ write heads. 7 Head-media optimization is critical when media are not matched to head writability. More media dependence was observed in TS heads with a single coil with less field strength but higher field gradient compared to TS heads with double coils. 8 Writability enhancement in the recording layer can further improve SNR but this enhancement needs to be optimized by thermal stability factor ͑K u V / kT͒, adjacent track erasure ͑ATE͒, and return field-induced partia...

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mentioning

confidence: 88%

mentioning

confidence: 97%

Effect of magnetic softness in a soft layer on media properties of hard/soft stacked composite perpendicular media

Jung

Malhotra

Acharya

et al. 2009

Journal of Applied Physics

Self Cite

View full text Add to dashboard Cite

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“…7,10,11 Multiple ECC structures with no SUL have been deposited onto 65-mm-diameter glass disks at room temperature using a dc magnetron sputtering system. The absence of the SUL and the use of a vibrating sample magnetometer ͑VSM͒ to sense both the outof-plane and in-plane component of the magnetization simultaneously, allows observing and quantifying the tilt of the SL magnetization during the field induced reversal.…”

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confidence: 99%

“…The hard granular magnetic layer ͑HL͒, namely CoPtCr-SiO x ͑14 nm͒ has a saturation magnetization of M s = 550 emu/ cm 3 and an anisotropy field of H kHL = 14 kOe. 7,10 In other words, as the SL thickness increases, the evolving difference of H c and H cr originates from a more incoherent and thus more reversible switching process. For the SL, we use a highly exchange-coupled CoPtCrB alloy, i.e., with a strong coupling between the grains, which is very different from the magnetically isolated grains in the HL.…”

mentioning

confidence: 99%

“…For the SL, we use a highly exchange-coupled CoPtCrB alloy, i.e., with a strong coupling between the grains, which is very different from the magnetically isolated grains in the HL. 5,7 As the SL thickness increases, one can observe a systematic increase in the H cr / H cr ͑0°͒ minimum value as well as a decrease in the field angle where the minimum occurs. All ECC media have been finally covered with an overcoat for protection against oxidation.…”

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confidence: 99%

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Revealing the reversible rotation of magnetization in exchange-coupled composite media switching

Hauet

Florez

Margulies

et al. 2009

Applied Physics Letters

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International audienceWe present a study of the magnetic reversal mechanism for exchange coupled composite perpendicular media, i.e., hard granular layer/exchange-coupling layer ͑ECL͒/soft layer ͑SL͒ systems, without soft underlayer. Using a vibrating sample magnetometer, the out-of-plane and in-plane components of the magnetization are monitored simultaneously, while sweeping an external out-of-plane magnetic field. The in-plane signal reveals the reversible rotation of the magnetization during the switching process. The amplitude of this rotation is correlated with the variations in coercivity and angular dependence of the remanent coercivity for different ECL and SL thicknesses. One of the main challenges currently faced by the hard disk drive industry is maintaining both writability and magnetic stability within magnetic volumes so small that the magnetic anisotropy energy responsible for stabilizing the direction of the magnetization becomes comparable to the energy of thermal fluctuations at room temperature. While for single layer perpendicular media, writability and stability are correlated through the magnetocrystalline anisotropy, it has been demonstrated in recent years that adding a soft magnetic layer ͑SL͒ to the usual hard granular layer ͑HL͒, in a so-called exchange-coupled composite ͑ECC͒ media can improve the writability-to-stability ratio. 1,2 Theoretical models have been developed for the proposed incoherent reversal process in ECC media 3,4 and several experimental demonstrations of the advantages of ECC media with respect to recording performance have been published. 5–9 Most of these reports focus on defining optimum properties for the SL as well as for the interfacial exchange-coupling between the HL and the SL. However, only a few experiments have been performed for the purpose of understanding the fundamental nature of the incoherent reversal or confirming the theoretical predictions in actual perpendicular media structures. Here we study an ECC system grown without a soft underlayer ͑SUL͒ in order to investigate the incoherent reversal process. The absence of the SUL and the use of a vibrating sample magnetometer ͑VSM͒ to sense both the out-of-plane and in-plane component of the magnetization simultaneously , allows observing and quantifying the tilt of the SL magnetization during the field induced reversal. We prepared a series of samples with different SL thicknesses in order to study the effect of SL thickness on the degree of magnetiza-tion tilt in the ECC system. Finally, we demonstrate the origin of the " reversibility " observed during the minor loop analysis reported in previous experiments. 7,10,1

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Effects of soft layer softness on the magnetic properties of perpendicular exchange-coupled nanocomposite films

Tang

Chua

Zhang

et al. 2011

Journal of Magnetism and Magnetic Materials

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Comparison of media properties between hard/soft stacked composite and capping layer perpendicular recording media

Cited by 7 publications

References 20 publications

Effect of magnetic softness in a soft layer on media properties of hard/soft stacked composite perpendicular media

Effect of magnetic softness in a soft layer on media properties of hard/soft stacked composite perpendicular media

Revealing the reversible rotation of magnetization in exchange-coupled composite media switching

Effects of soft layer softness on the magnetic properties of perpendicular exchange-coupled nanocomposite films

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