The dynamics of thermally activated reversal in elongated ferromagnetic particles is studied, A micromagnetic model is used which accomts for thermal fluctuations through the addition of a stochastic fluctwtioii field. Results are given approximating a particle of §:1 aspect ratio, with exchange length eqnal to particle radius, which is typical of current particulate media. Fast relaxation of the inagiietizatioii is observed. Thermal effective voliuiies inferred froiii our results can be significantly less than particle volumes.

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A simple energy surface model is introduced to explain single domain particle switching under sub-Stoner–Wohlfarth fields. The criterion is that if the initial energy exceeds the subsequent energy barrier maximum, then the particle can reverse. Reversal will occur only for small damping constants and short field rise times, so the magnetization dynamics explores a sufficiently large portion of the energy surface. The results are confirmed by micromagnetic analyses and are consistent with both large scale micromagnetic simulation and experimental data. This effect may be utilized for ultrahigh density (1 Tbit/in2) and ultrahigh data rate magnetic recording (>2 Gbit/s).

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ReuseUnless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. Abstract-With the move to recording densities up to and beyond 1 Tb/in 2 , the size of read elements is continually reducing as a requirement of the scaling process. The expectation is for read elements containing magnetic films as thin as 1.5 nm, in which finite size effects, and factors such as interface mixing might be expected to become of increasing importance. Here, we review the limitations of the current (micromagnetic) approach to the theoretical modeling of thin films and develop an atomistic multiscale model capable of investigating the magnetic properties at the atomic level. Finite-size effects are found to be significant, suggesting the need for models beyond the micromagnetic approach to support the development of future read sensors.Index Terms-Atomistic calculations, computational modeling, read elements.