ITE Technical Report
Online ISSN : 2424-1970
Print ISSN : 1342-6893
ISSN-L : 1342-6893
23.69
Showing 1-21 articles out of 21 articles from the selected issue
  • Type: Cover
    Pages Cover1-
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
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  • Type: Index
    Pages Toc1-
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
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  • Zheng Hu, Yu Han, Yi Chen
    Type: Article
    Session ID: VIR99-90
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    A new type of preparation method has been developed to produce nanoscale amorphous alloys. Iron-boron amorphous alloy particles thus obtained have boron contents far beyond the eutectic limitation of the binary system, and particle sizes around 10 nm corresponding to surface areas about 62 m^2/g. The unique properties of the products, which are not obtainable by any other preparation methods, and the applicability of the new method for mass-production suggest that this approach may provide a new class of nanoscale amorphous materials for various applications. Mossbauer spectroscopy and transmission electron microscopy were used to clarify the process of sample preparation.
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  • S. Wang, P.S. Lee, J. Ding, G.M. Chow
    Type: Article
    Session ID: VIR99-91
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Nickel thin films were deposited onto (100) silicon wafers using the sputtering technique. The thickness was varied between 45 to 500 nm. The nickel film formed in the initial stage (45 nm) was an uniform and continuous layer on the silicon substrate coated with a native silicon oxide layer. The film with a thickness of 78 nm exhibited high coercivity H_c (806 Oe) and high squareness in the perpendicular direction to the film plane, while H_c of 349 Oe was measured in the film plane. As the thickness increased, coercivity and magnetic anisotropy reduced and a plane anisotropy was finally exhibited in thick films (〜500 nm). TEM study showed that the films were mixtures of a columnar structure on the top and a uniform continuous structure on the bottom. All the films have shown a (111) texture and the grain size was estimated to be 15-20 nm.
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  • Daishun Zheng, Xiaohong Li, Tian Xie, Dongping Wu, Fulin Wei, Zheng Ya ...
    Type: Article
    Session ID: VIR99-90
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Fe-Ta-N films and Fe-Al-N films with different composition were prepared by RF reactive sputtering technique, using composite targets with Ar+N_2 mixed gases. The influences of Ta and Al content, sputtering partial nitrogen pressure P(N_2) and annealing temperature T_A on structure and magnetic properties of films were investigated. It is found that the addition of Ta and Al efficiently inhibits the formation of γ-Fe_4N phase in the films. A comparison of influences of additional Ta and Al elements on structure and soft magnetic properties of Fe-N based films was made and the mechanism is discussed in this paper.
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  • M. Lu, M. Matsumoto, F.L. Wei, Z.D. Hu, Z. Yang
    Type: Article
    Session ID: VIR99-93
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    The single domain size of ferromagnetic cubic particles are invesgated by micromagntics simulation. The angular dependence of coercive forces and the angular dependence of hysteresis loops for particles of sizes 250Å, 350Å, 450Å, 500Å, 520Å, 530Å and 550Å are calculated and discussed. For a particle of size smaller than 450Å, it switches mostly in the coherent rotation, for a particle of size 500Å, its magnetization reversal resembles the incoherent fanning, while for a particle of size larger than 520Å, its magnetization reversal is due to the wall motion. The single domain size for cubic particle is about 510Å.
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  • Dan Wei, C.K. Ong
    Type: Article
    Session ID: VIR99-94
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Medium noise is the dominant noise in ultra-high density disk recording systems. The peak, width and jitter noise are analyzed by micromagnetic simulation. Four different media, with a fixed grain size of 135Å and a coercivity of 2900 Oe, are chosen for medium noise analysis. The linear recording density is increased from 340 KFCI to 750 KFCI, while the area recording density is from 14.3 Gb/in^2 to 31.5 Gb/in^2. The peak-amplitude noise is studied by analyzing the distribution of the peak magnetization M_p in each bit. The distribution of M_p develops from a delta-function around the remanence M_γ at low densities to a flat distribution at extremely high densities. It is found that the transition a-parameter is no longer proportional to the square root of M_γδ, as given in the William-Comstock approximation. The peak jitter noise in the read back voltage is studied by the percentage of the transition jitter in a bit length.
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  • Weichun Ye, Bin Liu, Yu Lin
    Type: Article
    Session ID: VIR99-95
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    As the track becomes narrower, the effects of track edge become more significant. These effects, such as the amplitude reduction, variations in the shape of the isolated pulse, the partial erasure and the amplitude asymmetry, are dependent on head/disk combination and the off-track position. These relationships are discussed in detail in this paper. More importantly, an off-track model is proposed to study the off-track BER performance for the head with narrow track width. The BER performances of EPRML channel for different off-track cases and different head/media combinations are studied based on this model. Simulation results have proved that this model is a useful tool for simulation of system performance.
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  • E. Miyashita, K. Kuga, R. Taguchi, T. Tamaki, H. Okuda
    Type: Article
    Session ID: VIR99-96
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    It is known that amorphous continuous media such as TbFeCo show extremely low noise characteristics because of the structure of the continuous medium without grains. There is great interest in the use of amorphous media in magnetic recording. We investigated recording characteristics of the amorphous continuous medium by a computer simulation using the Landau-Lifshitz-Gilbert equation. It was shown that the transition of the continuous medium is very sharp and the noise level very low. It was also shown that recorded magnetization patterns of the continuous medium are distinct at high recording densities above 500 Gbit/inch^2. We concluded that the continuous medium has great potential for use in ultra-high density recording.
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  • Lianjun Wu, Naoki Honda, Kazuhiro Ouchi
    Type: Article
    Session ID: VIR99-97
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    A Co/Pd multilayer film with a perpendicular coercivity of 2.2 kOe and SQ of unity was prepared by electron beam evaporation in vacuum. In the MFM image for signal patterns of 4 kFRPI recorded using a ring type MIG head, many reversed domains were observed. However, when the film was magnetized along the film normal using an electromagnet(H=13 kOe), few reversed magnetic domains were observed, which was consistent with SQ=1. Therefore, the reversed domains in the signal patterns occurred in recording process. The dc erasing was also studied with the magnetic field inclined to the film normal. The domain structures were almost the same when the perpendicular components of the field were kept constant while the in-plane components were varied, implying that the in-plane field component did not contribute to the formation of the reversed domains. Reversed magnetic domains were easily induced even when a weak reversing magnetic field was applied along the film normal. Hence, the reversed magnetic domains in the signal patterns were considered to be caused by some erasing effect of the ring type MIG head. A large negative nucleation field in the perpendicular M-H loop is effective to suppress the reversed magnetic domains.
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  • Takahiro KUROSAWA, Naoki HONDA, Kazuhiro OUCHI
    Type: Article
    Session ID: VIR99-98
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Origins of baseline shift was discussed by the measured off-track properties using a wide write head and a narrow read head with track widths of 100μm and 2.7μm, respectively. The baseline shift became increased when the read head was moved close to the track edge. Beyond the track edge, baseline shift dropped to negative values. Simulating the stray field at the track edge and the sensitivity functions of the MR head along to the track width direction, it was assumed that the output from the stray field showed the same behavior as the baseline shift obtained experimentally. Sensitivity function of the MR head along the longitudinal direction was also determined. The sensitivity function of the MR head could express the sum of a double gap ring head component and a Lorentz peak. This Lorentz peak component gives the in-bit baseline shift originated from the stray field at the track edge.
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  • Masaru UCHIDA, Naoki HONDA, Kazuhiro OUCHI
    Type: Article
    Session ID: VIR99-99
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Although single layer perpendicular recording media with a smaller slope in the perpendicular M-H loop exhibit low noise properties, the media require a sharp head field to acquire high recording performance. Reducing of recording layer thickness would be effective for recording using a sharp head field distribution. Thus, effects of thickness on read/write performances were investigated for Co/Pd multilayer media. Normalized signal level increased with reducing in thickness, which was remarkable on recording for a small loop slope media and at higher densities. The thinner media could use a sharper head field to acquire a narrower dipulse width, but the recording resolution of the present media was determined under the influence of the magnetic domain structure and size.
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  • Bo Liu, Sheng-Bin Hu, Wei Zhang
    Type: Article
    Session ID: VIR99-100
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    As technology moves towards 100 Gb/in^2 areal densities and channel density above 3, the homogeneity of media's recording capability becomes a crucial issue in defining the reliability of the recording systems. Two concepts are proposed in this work for performance analysis : recording performance roughness analysis and dynamic magnetic roughness analysis. The recording performance roughness analysis is based on an in-situ measurement technique of the non-linear transition shift(NLTS). Relationship between the performance roughness and the roughness of dynamic magnetic parameters are studied. Results of experimental investigations indicate that the NLTS based performance roughness analysis can reveal more details on media's recording capability and the capability fluctuation. The work also extend to the accuracy analysis of the playback amplitude based methods for the analysis of the dynamic coercive squareness and dynamic hysteresis loop.
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  • Mui Chong Chai, Samuel Gan, Li Hong Zhang, Djohni Chandra, Quock Ng
    Type: Article
    Session ID: VIR99-101
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    A measure of head disk interface reliability is a better control of the nature and frequency of head disk contact. Intuitively, one strives to minimize the number and severity of those contacts in order to achieve maximal reliability. One approach to assess the relative goodness of a head/disk interface is by comparing the 'contact energy", determined by the area under the CSS friction profile, of that interface. Another approach is a detailed characterization of the contacts for those interfaces, by time frequency analysis. This paper discusses these approaches and our laboratory findings. Contact Energy will be derived and its relationship to durability, as may be determined from css testing, will be discussed. Characterization of the nature of head/disk contacts, and their possible effects, for different head/disk pairs, will be explored.
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  • Li Hong Zhang, Mui Chong Chai, Samuel Gan, Djohni Chandra, Quock Ng
    Type: Article
    Session ID: VIR99-102
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Head disk reliability consists of at least of the following : durability, friction/stiction, and chemical integrity. Component and/or drive based css testing has been often used as the sole evaluation tool for all the reliability concerns. We have resurrected the use of the drag test as a quick and simple evaluation tool for head disk durability. This approach seems appropriate in light of the fact that protective coating and lubricant film thick nesses are both decreasing in order to accommodate for the increase in areal density. In an attempt to keep the HDI closely resembling the product HDI the same slider and disk pairs are used at below take-off velocities. We will discuss our findings relative to the conventional css tests, as well as other un-anticipated findings. Our findings will show that drag testing can have predictive as well as diagnostic capabilities.
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  • Jiwen Wang, Bo Liu, Zhi-min Yuan, Jun Ding
    Type: Article
    Session ID: VIR99-103
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Slider-disk impact at high velocity may induce high flash temperature due to frictional heating. The maximum values of flash temperature depend on the impact area, the material properties and the operating conditions, and it can range from below 100℃(normal condition)to more than 1000℃(extreme condition). By the effect of thermal expansion among the layers of disk, the stress induced by flash temperature in the magnetic layer are calculated based on different disk substrates. From the inverse magnetostriction effect, its influence on the magnetic degradation has been investigated via micro-magnetic simulation. The results show that magnetic degradation could occur far below Curie temperature.
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  • Hyeong-Jun Kim, Kwon-Ku Cho, Seung-Ki Joo
    Type: Article
    Session ID: VIR99-104
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    NiFe(60Å)/Co(5Å)/Cu(60Å)/Co(30Å) pseudo spin valve (PSV) thin films were prepared on Cu(50Å)/Si(111, 4 degree tilt-cut) templates by a RF magnetron sputtering system and patterned into micron sized magnetoresistive random access memory (MRAM) cells using conventional optical lithographic processes. When the switching properties of PSV MRAM cells were investigated with respect to the cell geometry, the cells showed a few mV of output voltrage in constant 1 mA of sense current and much sensitive variation of switching thresholds of both soft and hard layers consisting of the cells. In order to reduce the switching thresholds of magnetic layers in micro cells, which is an obstacle of realization of a competitive MRAM device, a new approach has been introduced using the control of shape anisotropy of the cells. By an appropriate combination of two anisotropy terms, shape anisotropy of the cells and magnetocrystalline uniaxial anisotropy of sheet films, the switching threshold of NiFe(60Å)/Co(5Å) soft layer could be decreased from about 15 Oe to 5 Oe and the concept has been thought to be useful for a practical PSV MRAM device.
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  • Won-Cheol Jeong, Kwon-Ku Cho, Seung-Ki Joo
    Type: Article
    Session ID: VIR99-105
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Spin valves exchange biased by a Co/Ru/Co [Ru/Co/Cu/Co/Ru/Co/Cu/Si Substrate] were fabricated on 4 degree tilt-cut Si (111) substrate by RF magnetron sputtering method. When a Cu (50Å) underlayer was deposited prior to the formation of the spin valves, Co/Ru/Co and Co layers constituting spin valves have been developed uniaxial magnetic anisotropy in the direction of Si <112>. In case of a Co/Ru/Co with the same thickness of Co[synthetic antiferromagnet], spin valves with a 25 Å Cu spacer have showed giant-magnetoresistance ratio above 5% until the external magnetic field overcame the crystal anisotropy field originated from tilt-cut Si substrate. When arrived at critical field, Co/Ru/Co has displayed spin flopping phenomena as in the antiferromagnetic material. In making the thickness of Co in a Co/Ru/Co different[synthetic ferrimagnet], above spin flopping phenomena have disappeared. Instead, thinner Co layer has first reversed its magnetization and keeped the antiparallel state with the thicker Co layer.
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  • Yong-Jin Cho, Kwon-Koo Cho, Seung-Ki Joo
    Type: Article
    Session ID: VIR99-106
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    In this paper, spin-dependent tunneling junctions, in which the tunneling barrier Al_2O_3 is formed by depositing a 1〜3nm thick Al layer, followed by thermal exidation at room temperature in an O_2 atmosphere, were fabricated on 4° tilt (111)Si substrate in 3-gun magnetron sputtering system. The top and bottom ferromagnetic electrodes were Ni_<80>Fe_<20> and Co. A maximum Tunneling MR ratio of 14% was obtained in the junction of which insulating barrier thickness was 2nm. By increasing the tunneling voltage across the junction, maximum MR ratio reduced and finally showed no MR characteristics.
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  • Dong-Hwan Ahn, Kwon-Ku Cho, Seung-Ki Joo
    Type: Article
    Session ID: VIR99-107
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    The exchange coupling of NiMn/Co and Co/NiMn bilayers has been investigated. Stacking sequence of NiMn and Co was changed and the effect of Ta underlayer on exchange coupling was examined. NiMn top-structured sample showed higher exchange coupling field and it was found that Ta underlayer had better not be used in order to obtain higher exchange coupling, which is unlike NiFe/NiMn bilayers. Also, as a function of the thickness of Co and NiMn layers, magnetic properties of Co/NiMn bilayers have been investigated and explored
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  • Type: Appendix
    Pages App1-
    Published: November 10, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
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