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Listera S.J.,University of St. Andrews | Kohlbrecher J.,Paul Scherrer Institute | Venkataramanaa V.,University of St. Andrews | Thomsonc T.,University of Manchester | And 2 more authors.
International Journal of Materials Research

Perpendicular magnetic recording media based on CoCrPt-SiO x thin-films have been studied with polarised small angle neutron scattering (SANSPOL) to probe the local (sub-10nm) granular structure and its magnetisation distribution. SANSPOL is sensitive to the direction of the magnetisation vector in the grains over a size range of 1-100 nm. This allows the grain size dependent magnetic reversal process to be probed in the recording layer. SANSPOL data can be analysed both using numerical models and through comparison with the granular structure determined using transmission electron microscopy. In this paper we compare these two methods in detail and demonstrate that both approaches arrive at very similar conclusions. © 2011 Carl Hanser Verlag, Munich, Germany. Source

Briones J.,CNRS Jean Lamour Institute | Montaigne F.,CNRS Jean Lamour Institute | Hehn M.,CNRS Jean Lamour Institute | Lacour D.,CNRS Jean Lamour Institute | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics

We study the thermally induced depinning process of a single magnetic domain wall (DW) under applied field when the DW is trapped by a notch made in a nanowire shaped from a spin-valve multilayer with in-plane magnetization. In such devices depinning is typically a stochastic process and the depinning field distribution exhibits complex features. By analyzing simultaneously depinning field distributions and relaxation data, we observe two distinct sources of "complexity" in DW depinning processes: multiplicity in the DW structure and fundamental complexity in the depinning process. © 2011 American Physical Society. Source

Kalezhi J.,University of Manchester | Kalezhi J.,Copperbelt University | Greaves S.J.,Tohoku University | Kanai Y.,Niigata Institute of Technology | And 3 more authors.
Journal of Applied Physics

In bit patterned media (BPM), a magnetic data storage medium is patterned into nanoscale magnetic islands each representing one binary digit (bit). The recording performance of BPM depends upon the variability of island position, geometry, and magnetic characteristics. To understand the impact of the distributions of these parameters on the performance of BPM a detailed statistical model of write-errors has been developed. The islands can either be single layer or two-layer exchange coupled composite (ECC) structures. The modeling of ECC islands was made possible by the development of a 2-spin model to calculate switching field, coercivity, and energy barrier as a function of applied field which enables medium design to be optimized for a non-uniform write head field. The statistical model predicts coercivities and error rates in good agreement with a micromagnetic model but at significantly lower implementation and computational cost and shows good agreement with experimental data from drag-test experiments at 500 Gbit/in 2. The model enables the position tolerance of the write head to be determined from the magnetic characteristics of the write head and the storage medium and it is therefore a valuable system design tool. © 2012 American Institute of Physics. Source

Mate C.M.,Hitachi San Jose Research Center | Marchon B.,Hitachi San Jose Research Center | Murthy A.N.,CA Technologies | Kim S.-H.,CA Technologies
Tribology Letters

In this article, we explore the physical mechanisms for lubricant migration on recording head slider surfaces and how this migration leads to increased slider-disk spacing during disk drive operations. This is done using both a new experimental methodology, called the "droplet stress test," and through simulation. In our simulations, we compare the air shear-induced lubricant migration modeled either as viscous flow of a continuum liquid film with zero slip or as wind driven slippage of molecules across the surface. The experimental data are best fitted using the viscous flow model to determine an effective viscosity for the sub-nanometer thick lubricant films. This effective viscosity tends to be somewhat less than the lubricant bulk viscosity due to air shear promoting the slippage of lubricant molecules across the surface. Our experimental results also indicate that the potential spacing increase from the pickup of disk lubricant on the slider is limited by the mobile fraction of the dewetting thickness of the lubricant film on the slider. © 2009 Springer Science+Business Media, LLC. Source

Lister S.J.,University of St. Andrews | Thomson T.,University of Manchester | Kohlbrecher J.,Paul Scherrer Institute | Takano K.,Hitachi San Jose Research Center | And 7 more authors.
Applied Physics Letters

Polarized small-angle neutron scattering has been used to measure the magnetic structure of a CoCrPt-SiOx thin-film data storage layer, contained within a writable perpendicular recording media, at granular (<10 nm) length scales. The magnetic contribution to the scattering is measured as the magnetization is reversed by an external field, providing unique spatial information on the switching process. A simple model of noninteracting nanomagnetic grains provides a good description of the data and an analysis of the grain-size dependent reversal provides strong evidence for an increase in magnetic anisotropy with grain diameter. © 2010 American Institute of Physics. Source

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