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How the temperature can switch the magnetization of a nanoparticle

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The fast increase in the data storage of hard disk drives and magnetic memories needs smaller and smaller magnets. A crucial issue in this miniaturization process is the growing influence of the temperature on the devices. For example, the magnetization of a nanoparticle can spontaneously switch at room temperature, loosing the stored memory. A collaboration between physicists of the laboratory ‘Matériaux et Phénomènes Quantiques’ of the Paris Diderot University and the ‘Laboratoire de Physique des Solides’ of the Orsay University has allowed a better understanding of this thermally activated magnetization switching. Their discovery will be important for the design of future ultra-high density magnetic recording devices.

The physicists of the STM team in the laboratory ‘Matériaux et Phénomènes Quantiques’ have done experiments where they grow self-organized cobalt nanoparticles on a gold substrate. They have then measured the magnetic stability of these nanoparticles as a function of temperature and size in the range 2-7 nm. The result of their measurements is that the stability of the biggest particles is overestimated by a common model, first introduced in 1949 by the Nobel prize in Physics Louis Néel. Simulations done by the physicists of the ‘Laboratoire de Physique des Solides’ have shown that this model was indeed wrong as soon as spin waves could be thermally excited in the nanoparticle. Including these spin waves allows a good agreement with the experiments and will be important to make more reliable predictions on the thermal reversal of magnetization in nanoparticles.

En savoir plus :

“Spin-Wave-Assisted Thermal Reversal of Epitaxial Perpendicular Magnetic Nanodots”

S. Rohart1, P. Campiglio2, V. Repain2, Y. Nahas2, C. Chacon2, Y. Girard2, J. Lagoute2, A. Thiaville1, and S. Rousset2, Phys. Rev. Lett. 104, 137202 (2010)

Contact chercheur :

Vincent REPAIN,

Informations complémentaires :

1Laboratoire de Physique des Solides, UMR 8502 CNRS, Université Paris Sude
Site du laboratoire :

2Laboratoire Matériaux et Phénomènes Quantiques, MPQ, UMR CNRS 7162, Université Paris Diderot – Paris 7.