磁存储技术的研究

21世纪是信息的世界,人们掌握信息量的需求越来越高。在信息存储技术中,磁存储仍然是最重要的存储技术之一。为提高磁信息存储量,就必须不断减小用于记录信息的磁性颗粒的尺寸。但当尺寸减小到一定程度时,超顺磁效应就会影响到记录的磁信息的稳定性。所以研制新型高密度磁记录技术必须要注意介质的退磁场和稳定性的影响。目前商用硬盘的磁记录技术基本都采用垂直记录技术,一般可以获得超过200Gb／in^2记录密度。介绍新近发展起来的热辅助磁记录技术和图案化介质技术原理与优势。     

超高密度图案化磁信息存储介质的研究进展

信息存储的容量不断增大才能满足信息社会高速发展的需求。要提高磁信息存储的容量,就必须不断减小用于记录数据信息位的磁性颗粒的尺寸,但当尺寸减小到一定程度时,由于超顺磁效应将影响磁信息信息位的稳定性,所以必须开发新型高密度磁记录技术。目前,商用硬盘的磁记录技术正从传统的水平记录技术向垂直记录技术过渡,但正如业内人士指出那样,为了应对其它超高密度存储技术,如有机存储、光存储等的挑战,垂直记录技术只是磁信息存储技术向超高密度方向发展的一个“跳板“。展望2011年前后的新技术,希捷提出了“热辅助磁性写入“(heat-assisted magnetic recording)技术,该技术的实质是采用高矫顽力的磁性材料如铁铂合金作为记录介质,在信息写入时通过激光束加热降低信息位翻转场写入信息。而日立存储则提出“图案化介质“(patterned media)技术,在这种技术中,存储数据的信息位宛如“点“一样彼此相互独立,减少相互间的干扰和降低数据信息位损坏的危险。这两种技术都可望将磁信息存储密度提高到1Tbit/平方英寸以上,但是它们的实用化还有许多科学与工程问题需要解决。详细介绍了图案化介质记录技术的工作原理、读写存储系统的...     

γ—Fe_2O_3粒子在磁浆中的分散性及定向性

当前磁记录领域的重要课题是设法提高记录密度。提高记录密度的方法大致有以下几种:1)减少粒子尺寸;2)提高矫顽力,降低自减磁损失;3)增加粒子的填充密度,提高磁通密度,获得高输出;4)提高表面平滑性,减小间隙损失。1)～3)主要指磁性粒子本身特性,4)关系到磁浆和涂布技     

垂直磁记录技术

提高磁带和磁盘表面的信息贮存密度是当今磁记录研究和发展的方向。增加记录密度,有利于提高影像的解像力和实现记录数据化。垂直记录是提高记录密度的途径之一。信息记录密度取决于磁带、磁盘单位面积的磁通反转或转换的量以及检测信噪比的大小等。目前大多数记录介质都是通过将磁性颗粒均匀分散在粘合剂中而制得,故磁粉     

单分散磁性单晶铁氧体纳米颗粒的制备

近年来,小尺寸单分散磁性材料在磁流体、先进磁性器件、催化剂、颜料、高密度磁记录介质以及医学诊断等方面应用中显示出许多独特的性能及广泛的应用前景.因此,关于单分散纳米磁性颗粒的制备成为了基础科学技术方面学者们研究的热点课题.     

CoCr基磁性薄膜材料的研究现状和发展趋势

简要介绍了磁记录用介质膜的发展趋势及面临的问题,介绍了垂直记录方式的优点,综述了国内外对垂直磁记录用介质膜材料的分类及研究现状,回顾和评述了CoCr基磁性薄膜的研究现状和发展趋势.     

等离子体以及溶液反应法合成金属磁性纳米颗粒

当磁性材料尺寸进入纳米级时,颗粒尺寸与磁性材料的特征物理长度相当,如磁单畴尺寸、超顺磁性临界尺寸、交换作用长度以及电子平均自由路程等,磁性纳米材料就会呈现出与块状材料不同的磁学性质。氧化物磁性纳米颗粒的合成比较容易,这方面的研究比较成熟。金属磁性纳米颗粒的合成则要困难很多,所以金属磁性纳米颗粒的合成以及磁学性质一直是一个研究热点。对等离子体法和溶液反应法合成磁性金属纳米颗粒的研究,并对工作进行了简洁介绍。     

磁记录技术的发展

磁记录技术是一种利用磁性物质作记录、存储和再生信息的技术,它包括录音、录象以及数字信息存储。磁记录材料有磁卡、磁鼓、磁带、磁盘和磁泡等,目前用途最广、用量最大的是磁带。近年来随着电磁物理学和电子应用技术的发展,新型磁记录材料和记录技术不断涌现,有关磁盘和磁     

超高密度磁存储的展望

磁性存储是最常用的海量存储技术,其记录密度越来越高,发展也越来越快。本文通过对信息记录、读出和存储三个过程的分析,对比了硬磁盘记录、垂直磁记录和磁光记录的优缺点,指出了采用垂直记录模式、非晶结构合金薄膜或铁氧体薄膜介质是实现超高密记录的方向,光辅助磁记录是很有希望的记录技术。同时,还指出量子磁盘技术是未来高密记录的方向。     

La1-xSrxFeO3纳米微粉的微结构与磁性

为了研究La1-x Srx FeO3纳米微粉的成分及颗粒尺寸对其微结构及磁学性能的影响,采用溶胶-凝胶法制备了不同颗粒尺寸、不同Sr含量的钙钛矿型La1-x Srx FeO3(x=0～0.3)纳米微粉,采用X射线衍射和振动样品磁强计对其结构与磁性进行了分析.分析表明,所制样品均具有正交钙钛矿结构;对于颗粒尺寸相近、Sr含量不同的样品,随Sr含量增加,晶格收缩;在具有不同颗粒尺寸的La1-xSrx FeO3(x=0.3)纳米微粉中,随着颗粒尺寸的减小,晶格膨胀;La1-x Srx FeO3(x=0～0.3)纳米微粒具有弱铁磁性,Sr含量的增加导致自发磁化强度下降,且随着颗粒尺寸的减小,La1-x Srx FeO3(x=0.3)纳米微粉的自发磁化强度增大;由Sr的替代以及颗粒尺寸减小引起的结构变化导致磁性的变化.     

A new theory of recording media noise

Previous investigations of the noise in particulate or grainy recording media have considered statistical variations in the processes by which the particles become magnetized. The theory of noise presented includes also statistical variations in the packing density of the particles. An extremely simple analysis shows that, when both of these phenomena are included properly, the noise power of recording media may always be expected to depend upon the magnetization, or signal level, and the particle packing factor. It is found that the recording media should always provide higher signal-to-noise ratios (SNRs) than was previously supposed. It is pointed out that the signal recovery or detection techniques employed today in magnetic storage devices cannot yield optimum SNRs or bit error rates. Some algebraic and/or conceptual errors in the published literature on noise are discussed.<>     

Patterning of FePt for magnetic recording

Higher areal density for magnetic recording is needed to provide larger storage capacities on harddisk drives. However, as the recording bit size of traditional magnetic recording materials (such as Co/Cr) approaches 10 nm, the magnetic direction of each recording bit would become unstable at room temperature due to thermal fluctuation. To solve this problem, efforts have been made using two methods: one method is to replace the disk media with new materials possessing higher magnetic anisotropy which would lead to better thermal stability; and the second one is to employ different configurations for the recording layer. FePt with patterned media configuration is a combination of these two methods. In this paper we review some novel and interesting methods of patterning FePt for magnetic recording, including thermal patterning, self-assembly patterning, and lithography patterning.     

Magnetic-Pole Flip by Millimeter Wave

In the era of Big Data and the Internet of Things, data archiving is a key technology. From this viewpoint, magnetic recordings are drawing attention because they guarantee long-term data storage. To archive an enormous amount of data, further increase of the recording density is necessary. Herein a new magnetic recording methodology, “focused-millimeter-wave-assisted magnetic recording (F-MIMR),” is proposed. To test this methodology, magnetic films based on epsilon iron oxide nanoparticles are prepared and a focused-millimeter-wave generator is constructed using terahertz (THz) light. Irradiating the focused millimeter wave to epsilon iron oxide instantly switches its magnetic pole direction. The spin dynamics of F-MIMR are also calculated using the stochastic Landau–Lifshitz–Gilbert model considering all of the spins in an epsilon iron oxide nanoparticle. In F-MIMR, the heat-up effect of the recording media is expected to be suppressed. Thus, F-MIMR can be applied to high-density magnetic recordings.     

FePt nanocluster films for high-density magnetic recording

High anisotropy L1(0) ordered FePt thin films are considered to have high potential for use as high areal density recording media, beyond 1 Tera bit/in2. In this paper, we review recent results on the synthesis and magnetic properties of L1(0) FePt nanocomposite films. Several fabrication methods have been developed to produce high-anisotropy FePt films: epitaxial and non-epitaxial growth of (001)-oriented FePt:X (X = Au, Ag, Cu, C, etc.) composite films that might be used for perpendicular media; monodispersed FePt nanocluster-assembled films grown with a gas-aggregation technique and having uniform cluster size and narrow size distribution; self-assembled FePt particles prepared with chemical synthesis by reduction/decomposition techniques, etc. The magnetic properties are controllable through variations in the nanocluster properties and nanostructure. FePt and related films show promise for development as heat-assisted magnetic recording media at extremely high areal densities. The self-assembled FePt arrays show potential for approaching the ultimate goal of single-grain-per-bit patterned media.     

An investigation of the effects of media characteristics on read channel performance for patterned media storage

Many view data storage on patterned magnetic media as one way of attaining storage densities in excess of 1 Tb/in/sup 2/ and thus overcoming the problems associated with recording at ultrahigh densities on conventional continuous media. In this paper we investigate, through the use of a replay simulation developed to take into account the three-dimensional nature of the patterned media, the effects that the shape-constrained media have on the bit-error-rate performance of the read channel in 1-Tb/in/sup 2/ perpendicular recording. In particular, we analyze how media configurations with varying island shape, size, and distribution affect the channel performance.     

Perspectives for 10 terabits/in2 magnetic recording

Magnetic recording technology has come a long way, since the introduction of the first hard disk drives (HDD) in 1956. The areal density has grown by a factor of 200 million times and the HDD has stayed as a main candidate for mass storage of information. In order to maintain its lead over other competing technologies, HDD industry continues to invent several technologies. Having introduced perpendicular recording technology in the last 5 years, the industry is looking at introducing bit-patterned media or heat-assisted magnetic recording in the next five years. The researchers--looking at a longer term--are investigating 10 Tbits/in2 as the next major milestone. The issues and probable candidates for 10 Tbits/in2 magnetic recording technology are described from a material perspective.     

Theory of magnetographic printing

The magnetic force of attraction between a recording surface and magnetic particles (the "developer" or "toner") is analyzed. The recording medium is assumed to be magnetically hard, the toner particles to be magnetically soft. The distribution of recording magnetization is taken to be periodic in the interior of an image area and uniform in an image free area. The toner particles are assumed to be part magnetic, part nonmagnetic material. In most of the calculations it is assumed that the magnetic susceptibility of the toner particles is small compared to unity. In the interior of an image area the force density has primarily a component perpendicular to the recording plane. This component decreases exponentially with distance from the recording plane, if the distribution of magnetization is sinusoidal. Near the edge of an image area the force density also has a tangential component, but this is generally smaller than the normal component. For toner particles with similar internal structure the force per unit mass always decreases with increasing particle size. Considered as a function of recording wavelength (at constant particle size) it shows a maximum at a wavelength comparable to the particle diameter.The force acting on a small particle (simeq 10mum) in the immediate vicinity of the recording surface can be several hundred times the force of gravity. The implications of these results in regard to color printing are discussed.     

Remanence properties of substituted Ba-ferrite particles for highdensity magnetic recording

In this paper, the remanence properties of Co-Sn, Co-Ti and Co-Ti-Sn substituted Ba-ferrite (BaF) oriented particulate samples are compared with those of some oriented acicular particulate samples. A new parameter, the minor remanence distribution (MRD), is proposed to review the remanence properties of magnetic particles and the capabilities for resisting the recording demagnetization of magnetic recording media. It is shown that the MRD values of the oriented BaF particulate samples were smaller compared to oriented Co-γ-Fe₂O₃ samples, even though the squareness ratios (SR) of some of the BaF samples were smaller than those of the Co-γ-Fe₂O₃ samples. It Is the small MRD, SFD_r, IRS and large DH _r of a medium that can result in a large resistance to the effects of recording demagnetization and therefore in superior characteristics for high density magnetic recording. Since Co-Sn substituted BaF platelet-shaped particles exhibit these characteristics and have a very low temperature coefficient of coercivity, these particles can be expected to be a promising candidate for high density magnetic recording     

Recording on Bit-Patterned Media at Densities of 1 Tb/in$^2$and Beyond

We present a comprehensive analysis of the areal density potential of a bit-patterned media recording. The recording performance is dominated by written-in errors rather than traditional signal-to-noise considerations. Written-in errors are caused by statistical fluctuations of the magnetic properties and the locations of the individual dots. The highest areal densities are obtained with a combination of a pole head, a soft magnetic underlayer, and a storage medium of the composite type. Areal density scenarios of up to 5 Tb/in$^2$are analyzed.