Tailor-made nano-structured materials for perpendicular recording media and head—precise control of direct/indirect exchange coupling

Takahashi, M.; Tsunoda, Masakiyo; Saito, Shin

doi:10.1016/j.jmmm.2008.05.008

Cited by 5 publications

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References 45 publications

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“…Magnetic nanoparticles are of interest, both for fundamental reasons and by virtue of a variety of potential applications, ranging from ultrahigh density magnetic recording to biomedical applications. [1][2][3] Particularly, the study of bimagnetic core/shell nanoparticles, where both the shell and the core are magnetic, is steadily increasing, since one of the striking discoveries in magnetism made more than 50 years ago during the study of surface oxidized particles of cobalt, which was the observation of hysteresis loops substantially shifted away from zero field. 4,5 This phenomenon is known as the exchange bias (EB) effect, resulting from the direct exchange at the interface between ferromagnetic (FM) and antiferromagnetic (AFM) layers and/or nanoscale heterostructures.…”

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confidence: 99%

Surface-anisotropy and training effects of exchange bias in nanoparticles with inverted ferromagnetic-antiferromagnetic core-shell morphology

2011

Journal of Applied Physics

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A modified Monte Carlo method using the Metropolis algorithm is performed to simulate the hysteresis behaviors of the nanoparticles with an inverted antiferromagnetic (core)/ferromagnetic (shell) morphology at low temperature after field cooling. We have examined the dependence of exchange bias on the hard ferromagnetic surface anisotropy and the training effect. Our simulations reveal that, besides the antiferromagnetic core, another pinning source, namely, the hard ferromagnetic surface, can also contribute to the exchange bias in such a special structure. Above a critical surface anisotropy, the exchange bias field has a steep increase by means of the change of the magnetization reversal mechanisms, which are affected by the surface anisotropy. During the consecutive hysteresis loops, the exchange bias field decreases gradually to a constant value. The phenomena have been interpreted well by considering the combination of locking, releasing, and stabilizing of the spins on the antiferromagnetic core surface and the energy competition between Zeeman and antiferromagnetic anisotropy. Our results are in good agreement with the experimental findings.

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confidence: 99%