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Date Oct. 31 2012-Nov. 2 2012

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Displaying Results 1 - 25 of 128
  • Covers

    Publication Year: 2012 , Page(s): c1 - c4
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  • Table of contents

    Publication Year: 2012 , Page(s): 1 - 14
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  • Author index

    Publication Year: 2012 , Page(s): 1 - 6
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  • Top-down and bottom-up approaches to high-density bit-patterned media

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (511 KB) |  | HTML iconHTML  

    We develop processes relevant to bit-patterned media (BPM) to achieve nanostructures with densities of up to 4.4 Tdots/in2 using a combination of top-down electron-beam lithography and bottom up self assembly of Au nanoparticles. Evaluation of magnetic bits were performed on purely top-down approaches using both direct-deposition and ion milling processes. Measurements of BPM performance were performed to investigate the effects of trench material, and process conditions. View full abstract»

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  • 5 Tdot/inch2 bit-patterned media fabricated by directed self-assembling polymer mask

    Publication Year: 2012 , Page(s): 1 - 2
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    FePt bit-patterned media (BPM) was fabricated with a self-assembled polymer mask with 12 nm pitch (equivalent to 5 Tdot/inch2). A 3.2 nm FePt film with high c axis crystal orientation was prepared for the magnetic recording layer. Solvent vapor annealing was applied for uniform directed self-assembling of PS (polystyrene) - PDMS (polydimethylsiloxane) diblock copolymer. Pattern transfer from a polymer mask to FePt layer was achieved by employing a C hard mask. In spite of excellent magnetic characteristics of FePt layer, the fabricated FePt BPM showed small coercivity (Hc) of 6 kOe and large switching field distribution (SFD) of 21%. These results are due to the etching damage of FePt dots. Disordering of FePt L10 phase by the etching damage reduced magnetic anisotropy energy (Ku). View full abstract»

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  • Heat absorption model and media thermal design for HAMR

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (684 KB) |  | HTML iconHTML  

    In HAMR recording system, the thermal profile in recording medium is the key factor to determine the writing process. This work has developed the heat absorption model for composite materials of grains and grain boundaries. Besides the (n, k) values of recording layer itself, the optical constant of intermediate layers can vary the heat absorption rate in a big range. It is very important in the thermal design of HAMR recording media. View full abstract»

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  • Understand SNR limit and area density capability in HAMR

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1034 KB) |  | HTML iconHTML  

    Heat, or thermal, assisted magnetic recording (HAMR or TAMR), has become a strong candidate as the new recording scheme for future hard disk drive technology. In depth understanding the detailed recording processes and the performance correlation with all the important recording parameters and medium properties is of critical importance for the practical realization of its intended advantages at ultra-high area recording densities. This paper is dedicated to this purpose and the study is carried out via micromagnetics based recording simulation, utilizing the Landau-Lifshitz-Bloch Equation for modeling the medium behavior near Curie temperature. The medium is a single magnetic layer of FePt-Llo grains with non-magnetic grain boundaries. For clarity purpose in recording analysis, the thermal profile of the heating spot is assumed to be Gaussian in the down track direction and uniform in the cross-track direction so transition front will be straight rather than curved. The recording head field is assumed to be spatially uniform at a fixed angle of 45° with respect to the perpendicular axis. Thermal agitation field to each magnetic grain is included in simulating the recording process, according to the fluctuation-dissipation theorem. View full abstract»

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  • Improvement of magnetic force microscope resolution and application to high-density recording media

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (771 KB) |  | HTML iconHTML  

    Effects of magnetic material, coating thickness, and tip radius on magnetic force microscope (MFM) resolution have been investigated. MFM resolutions better than 8 nm have been confirmed with tips coated by high-magnetic moment materials with optimized thicknesses. High-resolution tips are applied to the observations of recorded magnetization structures of perpendicular and bit-patterned media samples. View full abstract»

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  • High coercive L10 FePt-X granular films with small opening-up of in-plane hysteresis loop by using conductive TiN intermediate layer

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (485 KB) |  | HTML iconHTML  

    The effects of a TiN intermediate layer on the microstructure and magnetic properties of the FePt films were investigated. With introducing TiN intermediate layer the chemical ordering and magnetic properties of FePt films significantly improved. The FePt film with 5nm TiN exhibited a large perpendicular anisotropy and smaller opening-up of in-plane hysteresis loop with out-of-plane coercivity of 13.7 kOe and in-plane coercivity of 0.24 kOe. Moreover, with doping C and SiOx, FePt film with coercivity around 20 kOe, a single layer structure, and small FePt grain size of 5.6 nm in average diameter was obtained. View full abstract»

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  • Highly (001)-oriented thin continuous L10 FePt films for bit patterned media

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB) |  | HTML iconHTML  

    We demonstrate a highly (001)-oriented thin continuous FePt film by introducing an FeOx cap layer. The agglomeration in capped FePt films is significantly suppressed by inhibiting the surface diffusion, which then yields a desired continuous film with a narrowed (001) out-of-plane angular distribution. Through the promoted interdiffusion of Fe and Pt by the reduction of Fe oxides during annealing, we successfully maintain a (001) L10 phase while suppressing the agglomeration in FePt films. By utilizing this continuous FePt film and template of diblock copolymer, we obtain FePt dot arrays with an average dot diameter of 25 nm. View full abstract»

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  • In-line sputter system prepared L10 ordered FePt granular film for HAMR application

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (470 KB) |  | HTML iconHTML  

    The FePt base composite films for HAMR application have been developed by using the in-line sputter system. The microstructure development of the FePt based HAMR media as a function of film thickness was investigated. It was found that for fixed doping concentration, the grain size slightly increases with the increasing film thickness. The well-isolated FePt grains with main grain size of 6.4 nm ±0.6 nm were obtained for 6 nm FePt-C film. The developed FePt-C composite film with well-isolated FePt grains has the potential to be used as the recording media for HAMR application. View full abstract»

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  • Vibration and noise in a HDD spindle motor originated from the axial asymmetry of magnetic design

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1283 KB) |  | HTML iconHTML  

    This research investigates numerically and experimentally the characteristics of axial unbalanced magnetic force (UMF) due to axial asymmetry of magnetic design in the spindle motor of a hard disk drive, and its effect on the acoustic noise and vibration. It shows that the least common multiple (LCM) harmonic of pole and slot of the acoustic noise and vibration are originated from axial UMF. It also shows experimentally that the axially balanced magnetic design can minimize the LCM harmonics in acoustic noise and vibration. View full abstract»

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  • Extraction of bearing coefficients of fluid-dynamic bearing spindle motors

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1687 KB) |  | HTML iconHTML  

    In this digest, we report significant improvements over the method developed by Shen et al. [1] to extract bearing coefficients of a fluid-dynamic bearing (FDB) spindle motor in hard disk drives (HDD). An exact formulation is developed to extract bearing coefficients. Angular and radial displacements are measured to improve accuracy. Bearing coefficients are extracted successfully via three rounds of experiments. View full abstract»

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  • Analysis of dynamic characteristics of stamped base for 2.5 inch HDD

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1187 KB) |  | HTML iconHTML  

    In this study, stamped base with cold rolled steel plate was suggested for 2.5 inch hard disk drive (HDD). The stamped base has some benefits on the cost, manufacturing and thin form factor. On the other hand, low stiffness was expected because of sheet metal structure. Therefore, possibility of stamped base for 2.5 inch HDD was investigated in the view points of manufacturing process and dynamic characteristics. View full abstract»

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  • Simulation of a piezoelectric sensor array for slider-level contact detection

    Publication Year: 2012 , Page(s): 1 - 2
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (820 KB) |  | HTML iconHTML  

    A piezoelectric sensor array deployed on the trailing side of the slider was investigated for its capability in head-disk contact detection. Harmonic and transient responses were obtained by finite element analysis. Performance of the triple-sensor array was compared with that of a single sensor configuration. Under excitation of a typical contact force, output voltages of the sensor array of the millivolt level were observed in the simulation. View full abstract»

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  • A spinstand study in determining the optimum shingling percentage for shingled write recording

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (263 KB) |  | HTML iconHTML  

    Shingle write recording has recently received attention from many researchers as it is one of the candidates to extend the perpendicular magnetic recording. In this paper, we determine and propose the optimum shingling percentage by using various write width samples and various shingling or overlapping track pitches experimentally. We study the performance characteristics of key parameters that would affect the write ability of the shingled write recording. View full abstract»

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  • Thermoreflection measurement of magnetic thin films

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (297 KB) |  | HTML iconHTML  

    With recent developments in Heat Assisted Magnetic Recording (HAMR), there is growing intense interest in the thermal-optical properties of the HAMR media. We detect the phase change of the optical beam as it reflects from a FePt thin film under strong thermal gradient by carrying out Close-Aperture reflection Z-scan experiments. It was found that the far field spatial distribution of the reflected beam is sensitive and dependent on the thermal field distribution in the media. This experiment technique can be extended to study the spatial distribution of the thermal field in the HAMR media and to enable temperature measurement of HAMR media under laser irradiation. View full abstract»

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  • Thermal effect of a thin overcoating layer subject to laser heating

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (349 KB) |  | HTML iconHTML  

    This paper concerns the effect of a thin overcoating layer on the temperature increase in heat-assisted magnetic recording disk structure induced by laser heating. The optical absorption model, which derived from Maxwell's equation, is applied to quantify local energy absorption by the media. The numerical simulations indicate that the presence of a 2-nm overcoating layer results in additional 5% temperature increase in the disk, compared with that without overcoating layer. The temperature gradient between the overcoating layer and its neighbor layer is negligible small. The present study indicates that besides its mechanical properties, the thermal and optical properties of the overcoating material are important design factors. View full abstract»

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  • Long-ranged order cylindrical block copolymer thin films in un-patterned substrates

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1036 KB) |  | HTML iconHTML  

    The microdomain orientation in thin films of cylinder- and lamella- forming polystyrene-block-polymethyl methacrylate (PS-b-PMMA) copolymers on functional poly (styrene-r- methyl methacrylate) P(S-r-MMA) or polystyrene (PS) brushed substrates was studied using field emission scanning electron microscopy (FE-SEM). In order to prepare a well-ordered block copolymer nanotemplate in an equilibrated morphology the substrate material must have reactive functional groups for surface modification as well as extremely low surface roughness. The surface functionality is given by the reactive hydroxyl group at the oxides surfaces. The reactive hydroxyl group could be controlled by modifying in surface cleaning process. The homogeneity of patterned area was increased from about 300 nm to >;6 μm after 5 min ultraviolet ozone treatment. View full abstract»

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  • TiN and TiC interlayers for FePt-C based magnetic recording media

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (870 KB) |  | HTML iconHTML  

    Conductive TiN and TiC interlayers were utilized to promote epitaxial growth of (001)-textured FePt in place of the traditional non-conductive MgO interlayer. The film structure was given as Glass/CrRu/(TiC or TiN)/FePt-C. The films were fabricated under constant deposition temperature of 350°C for all three layers. Both TiN and TiC were capable of inducing (001)-textured FePt with square magnetic hysteresis loops and out-of-plane coercivity of up to 4kOe. Further increase in FePt recording layer deposition temperature to 500°C resulted in monotonic increase in coercivity of up to 9kOe whilst still maintaining strong perpendicular anisotropy, large magnetic squareness, and a small in-plane component. Subsequent doping of up to 40 vol. % C in FePt led to further increases in coercivity beyond 15kOe together with reduction in intergranular lateral exchange coupling. View full abstract»

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  • Effects of substrate bias with recording layer on perpendicular magnetic media

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (502 KB) |  | HTML iconHTML  

    A direct current (DC) bias is added on the substrate during the deposition of the recording layer of perpendicular magnetic recording media. It has been found that the bias has significant effects on the magnetic properties, such as coercivity, nucleation field, squareness, and domain size, and microstructure, such grain size, grain size segregation, and c-axis orientation. It is also observed that the roughness of the surface is reduced by using the bias. The mechanism of the bias effect is discussed. View full abstract»

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  • Micromagnetic study of a single-domain grain dynamics in magnetic recording media

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (254 KB) |  | HTML iconHTML  

    This work reports a micromagnetic study of relaxation and switching of a single-domain-grain magnetization in the effective magnetic field of recording media. Based on the modified Landau-Lifshitz equation of micromagnetic dynamics, we have computed the relaxation time as a function of material-dependent constants of the magnetization precession damping, which is attributed in our model to the coupling between magnetization-vector and stress-tensor of magnetic anisotropy of recording media. We found that the recording media characterized by parameters, revealed in presented simulations, can respond to ac microwave field by ultrafast relaxation and switching in picoseconds regime. View full abstract»

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  • Two-dimensional partial response maximum likelihood at rear for bit-patterned media

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (993 KB) |  | HTML iconHTML  

    Compared with conventional partial response maximum likelihood (PRML), we propose new structure of two-dimensional (2D) PRML for bit-patterned media storage. The proposed PRML at rear shows superior bit error rate performance despite no iteration in 2D soft output Viterbi algorithm. View full abstract»

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  • Two-dimensional soft output Viterbi algorithm with dual equalizers for bit-patterned media

    Publication Year: 2012 , Page(s): 1 - 2
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1011 KB) |  | HTML iconHTML  

    This paper proposes a two-dimensional detection method using dual equalizers for bit-patterned media storage. The proposed method has improved bit error rate performance with low computational complexity. View full abstract»

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  • Piezoelectric ZnO thin films for contact sensing and head actuation

    Publication Year: 2012 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (570 KB) |  | HTML iconHTML  

    This paper presents deposition and characterization of zinc oxide (ZnO) thin films for smart sliders. ZnO thin films with two different c-axis orientations were prepared using RF magnetron sputtering. A piezoelectric ZnO sensor array was fabricated using fabrication techniques compatible with standard slider micromachining process. View full abstract»

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