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High repetition granular Co/Pt multilayers with improved perpendicular remanent magnetization for high-density magnetic recording

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Chinese Physics B 2023年第2期32卷 405-410页

作者：李智张昆杜奥张洪超陈伟斌徐宁郝润润颜世申赵巍胜冷群文 Fert Beijing Research Institute MIIT Key Laboratory of Spintronics School of Integrated Circuit Science and EngineeringBeihang UniversityBeijing 100191China Beihang–Goertek Joint Microelectronics Institute Qingdao Research Institute Beihang UniversityQingdao 266101China School of Physics State Key Laboratory of Crystal Materials Shandong UniversityJinan 250100China

Thanks to the strong perpendicular magnetic anisotropy(PMA), excellent processing compatibility as well as novel spintronic phenomenon, Co/Pt multilayers have been attracting massive attention and widely used in magnetic ***, reversed magnetic domains come into being with the increasing layer repetition ‘N’ to reduce magneto-static energy, resulting in the remarkable diminishment of the remanent magnetization(Mr). As a result, the product of Mrand thickness(i.e., the remanent moment-thickness product, Mrt), a key parameter in magnetic recording for reliable data storing and reading, also decreases dramatically. To overcome this issue, we deposit an ultra-thick granular [Co/Pt]80multilayer with a total thickness of 68 nm on granular SiNxbuffer layer. The Mrt value, Mrto saturation magnetization(Ms) ratio as well as out of plane(OOP) coercivity(Hcoop) are high up to 2.97 memu/cm^(2), 67%, and 1940 Oe(1 Oe = 79.5775 A·m^(-1)),respectively, which is remarkably improved compared with that of continuous [Co/Pt]80multilayers. That is because large amounts of grain boundaries in the granular multilayers can efficiently impede the propagation and expansion of reversed magnetic domains, which is verified by experimental investigations and micromagnetic simulation results. The simulation results also indicate that the value of Mrt, Mr/Msratio, and Hcoopcan be further improved through optimizing the granule size, which can be experimentally realized by manipulating the process parameter of SiNxbuffer layer. This work provides an alternative solution for achieving high Mrt value in ultra-thick Co/Pt multilayers, which is of unneglectable potential in applications of high-density magnetic recording.

关键词： granular Co/Pt multilayers perpendicular magnetic anisotropy remanent moment-thickness product magnetic recording

magnetic property and recording performance of chemical deposition CoP thin films

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Rare Metals 2012年第3期31卷 260-263页

作者： Wang, Haicheng Zhou, Qunfei Teng, Jiao Wang, Lijin Yu, Guanghua Department of Material Physics and Chemistry University of Science and Technology Beijing Beijing 100083 China

The thickness of CoP thin films prepared by wet chemical deposition is of crucial importance on magnetic property and recording perform-ance. The coercivity of CoP films decreased with increasing film thickness. The coercivity was 45.37 kA m 1 at the thickness of 300 nm, and decreased to 21.65 kA m 1 at 5.7 μm. recording performance tests indicate that, for drums with the same size, different recorded magnetic pole density have different thickness requirements. For 40 mm diameter magnetic drum, the optimal CoP thickness is 3～10 μm for 256 re-corded magnetic poles, 1～2 μm for 512 recorded magnetic poles, and 500～800 nm for 1024 recorded magnetic poles.

关键词： CoP thin films magnetic property magnetic recording

A Novel High Code Rate Runlength Limited Coding Method for magnetic recording Channel

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A Novel High Code Rate Runlength Limited Coding Method for M...

Extended Kalman Filter based Acquisition Timing Recovery for magnetic recording Read Channels

2011 International Conference on Computer Science and Information Technology(ICCSIT 2011)

作者： Chun Liu Changsheng Xie Guangxi Zhu Qingdong Wang Dep. of computer science HUST

ISBN: (纸本)9781612848334

In this paper we present a novel high rate run length limited coding scheme for magnetic recording channel. The coding scheme splits the source data into sub-blocks, and constructs the encoding table of the sub-blocks as well as queuing rules of the indicating blocks, which can approach the maximum of RLL codes rate within the limits of special (d, k) conditions. Moreover, with the expansibility of the coding scheme, a higher rate RLL codes can be iteratively designed. As an illustration, a 32/33 (0, 6) RLL code is designed. Further an intersecting insert skill is used to design a 64/65 (0, 10) code based on the former encoder. Both the error propagation characteristic and the implementing method of the coding scheme are discussed.

关键词： magnetic recording RLL Code High Rate

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Extended Kalman Filter based Acquisition Timing Recovery for...

Below-diffraction-limited hybrid recording using silicon thin film super-resolution structure

2008 IEEE International Conference on Communications(ICC 2008)

作者： Euiseok Hwang Rohit Negi B.V.K.Vijaya Kumar Data Storage Systems Center（DSSC） Carnegie Mellon University PittsburghPA 15213-3890

In synchronous timing recovery approaches often employed in magnetic recording readback channels,the timing error detector（TED） output is assumed to be linearly related to the underlying phase ***,the noisy readback signal samples in high-density magnetic recording systems are nonlinearly related to the underlying timing ***,a nonlinear state space models may describe such systems more accurately and an improved timing recovery solution may be obtained via an extended Kalman filter（EKF） *** this paper,EKF based timing recovery is investigated for the acquisition *** simulations indicate that the EKF based timing recovery scheme yields smaller root mean square（RMS） error in timing estimates,which enables it to handle larger timing errors more *** addition,the proposed method converges faster than the conventional timing recovery schemes,which may allow us to reduce the length of the preamble pattern used for the acquisition.

关键词： Timing magnetic recording Frequency estimation Error correction Phase locked loops Signal processing Kalman filters Error correction codes Finite impulse response filter Detectors

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Chinese Physics B 2009年第12期18卷 5370-5374页

作者：焦新兵魏劲松干福熹 Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences

We report on new experimental results for below-diffraction-limited hybrid recording. In our experiments, by means of focused laser assisted magnetic recording, the magnetic domains within TbFeCo thin films are obtained under an external perpendicular direct magnetic field. For a single magnetic medium, the domain size is mainly determined by the focused spot, which is about 620 nm for the laser wavelength λ=406 nm, and a numerical aperture of the lens of 0.80. However, when a silicon thin film structure is inserted between the substrate and the magnetic medium, the recording domains can be reduced obviously. By optimizing the experimental condition, even the size can be reduced to about 100 nm, which is below the diffraction limit, i.e. about 1/6 of the spot size. This is very useful for improving the hybrid recording density in practical applications.

关键词： hybrid recording super-resolution magnetic recording

Performance of switch between exchange bias and coercivity:Influences of antiferromagnetic anisotropy and exchange coupling

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Journal of Materials Science & Technology 2022年第25期120卷 186-195页

作者： Ruijun Li Fan Zhang Yong Hu Department of Physics College of SciencesNortheastern UniversityShenyang 110819China State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China Department of Logistics Management Liaoning Provincial College of CommunicationsShenyang 110122China

The study on temperature dependence of exchange bias field and coercivity is crucial to solving the writing/reading dilemma in magnetic *** by recent experimental findings,a complete switch between exchange bias field and coercivity with temperature is proposed,and the performance,characterized by average switching temperature(T_(S))and switching temperature width(T_(W)),controlled by antiferromagnetic anisotropy(KAF)and exchange coupling(J_(AF))constants is studied based on a MonteCarlo *** results show that a linear relationship between T_(S)and KAFis established when KAFis above a critical value,while T_(S)is weakly influenced by J_(AF).On the contrary,T_(W)is insensitive to KAF,while strongly depends on J_(AF).Besides overcoming thermal energy,the increase of KAFfor a small J_(AF)guarantees the completely frozen states in the antiferromagnetic layers during magnetizing at higher temperature,below which the exchange bias field exists with a negligible ***,for a large J_(AF),the uncompensated antiferromagnetic magnetization behavior during the ferromagnetic magnetization reversal becomes complicated,and the switching process in the low temperature range depends on the irreversibility of uncompensated antiferromagnetic magnetization reversal during magnetizing,while in the high temperature range mainly influenced by the field-cooling process,resulting in a large T_(W).This work provides an opportunity to control/optimize the performance of the temperatureinduced switch between unidirectional and uniaxial symmetries through precisely tuning KAFand/or J_(AF)to meet different application demands in the next generation information technology.

关键词： magnetic recording Ferromagnet/antiferromagnet multilayer Exchange-bias/coercivity switch Temperature dependence Antiferromagnetic anisotropy Antiferromagnetic exchange coupling Monte-Carlo simulation

Controlled synthesis of monodispersed spherical ruthenium powders

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Rare Metals 2023年第12期42卷 4246-4254页

作者： Feng-Shuo Xu Hao Cui Man-Men Liu Jia-Lin Chen Ming Wen Chuan-Jun Wang Wei Wang Song Li Xu-Dong Sun Shao-Hong Liu Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education) School of Materials Science and EngineeringNortheastern UniversityShenyang 110819China State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum Metals Yunnan Precious Metals Laboratory Co.Ltd.Kunming 650106China

Monodispersed spherical Ru powders are essential for fabricating high-performance Ru sputtering targets,which have applications in very-large-scale integration circuits and magnetic recording ***,the synthesis of such powders remains a major ***,we reported the synthesis of monodispersed spherical Ru powders through controlling the molar ratio of SO_(4)^(2-)to Ru^(3+)in urea homogeneous precipitation solution and the annealing *** the addition of(NH4)2SO_(4)into the reaction solution,only gel-like precipitation particles were *** introducing(NH_(4))_(2)SO_(4) into the reaction solution and controlling the molar ratio of SO_(4)^(2-)to Ru3+between 0.50 and 1.00,monodispersed spherical precursor powders were *** nucleation and growth of monodispersed spherical precursor particles in solution were found to conform to LaMer's *** controlled annealing at 450℃in a hydrogen atmosphere,the obtained metallic Ru powder with an average particle size of 135 nm inherited the spherical morphology and excellent dispersity from the monodispersed spherical precursor *** results and findings would deepen the understanding of the preparation of monodispersed Ru and Ru-like powders.

关键词： Ruthenium Sputtering target Spherical powder Integration circuits magnetic recording

Effects of annealing temperature and time on microstructure and magnetic properties of Pr-Co thin films

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Rare Metals 2012年第2期31卷 121-124页

作者： Li, Zhi Ding, Hao Zhang, Jun Wang, Hanbin Wang, Hao Faculty of Physics and Electronic Technology Hubei University Wuhan 430062 China

A series of Pr-Co thin films were deposited on the Si (100) substrates with Cr underlayer by magnetron sputtering. The effects of both the post-annealing temperature and the annealing time on the microstructure and magnetic properties for the Pr-Co films were studied systemati- cally. The as-deposited Pr-Co thin films are mostly amorphous and tend to crystallize after annealing at temperatures above 600 C. When the annealing time is increased, the films show a complicated structure with various phases coexisting. Accordingly, the as-deposited film and low temperature annealed films are soft magnets and films annealed at temperatures beyond 600 C tend to be hard magnets. When the annealing time is increased from 5 min to 2 h, the films transfer from hard magnets to soft again. The sample annealed at 600 C for 10 min shows the largest coercivity of 0.59 T.

关键词： Pr-Co coercivity magnetic recording

Design of internal Brewster guided-mode resonance filter

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Chinese Optics Letters 2009年第6期7卷 462-464页

作者：傅小勇易葵邵建达范正修 Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai 201800 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

An internal Brewster guided-mode resonance （GMR） filter is designed. For this kind of GMR filter, the Brewster reflection occurs at the interface of grating/waveguide layers rather than at the interface of air/grating layers. At Brewster angle of 60~, the GMR filter owns almost 100% reflection at the resonance wavelength of 800 nm with the full-width at half-maximum （FWHM） of 0.2 nm. Its angle response changing with the fabrication deviation is also discussed.

关键词： Giant magnetoresistance magnetic field effects magnetic recording