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On beating the superparamagnetic limit with exchange bias. R. F. L. Evans1, R. Yanes2, O. Mryasov3, R. W. Chantrell1 and O. Nature. Jun 19;() Beating the superparamagnetic limit with exchange bias. Skumryev V(1), Stoyanov S, Zhang Y, Hadjipanayis G, Givord D. Request PDF on ResearchGate | On beating the superparamagnetic limit with exchange bias | Interest in magnetic nanoparticles has increased.

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Whereas the cobalt cores lose their magnetic moment at 10 K in the first system, they remain ferromagnetic up to about K in the second. As a federation of National Physical Societies, the EPS studies issues of limi to all European countries relating to physics research, science policy and education.

Beating the superparamagnetic limit with exchange bias – Dimensions

Evans et al EPL 88 When this happens, the thermal fluctuations induce random flipping of the magnetic moment with time, and the nanoparticles lose their stable magnetic order and become superparamagnetic. Here we show that magnetic exchange coupling induced at the interface between ferromagnetic and antiferromagnetic systems can provide an extra source of anisotropy, leading to magnetization stability.

Such a system is ideal for thermal stability since there is no energetically stable reversed state, providing the antiferromagnetic shell is unchanged. Thus, the demand for further miniaturization comes into conflict with the superparamagnetism caused by the reduction of the anisotropy energy per particle: It has a worldwide membership of around 50 comprising physicists from all sectors, as well as those with an interest in physics. In order to investigate the possibility of “beating the superparamagnetic limit with exchange bias” Skumryev V.


Beating the superparamagnetic limit with exchange bias

It works to advance physics research, application and education; and engages with policy makers and the public to develop awareness and understanding of physics. Click here to close this overlay, or press the “Escape” key on your keyboard. Its publishing company, IOP Publishing, is a world leader in professional scientific communications. Interest in magnetic nanoparticles has increased in the past few years by virtue of their potential for applications in fields such as ultrahigh-density recording and medicine.

Yanes 2O. We demonstrate this principle for ferromagnetic cobalt nanoparticles of about 4 nm exchante diameter that are embedded in either a paramagnetic or an antiferromagnetic matrix. Most applications rely on the magnetic order of the nanoparticles being stable with time.

This behaviour is ascribed to the specific way likit nanoparticles couple to an antiferromagnetic matrix. As a learned society, the EPS engages in activities that strengthen ties among the physicists in Europe.

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For systems with large values of the interfacial coupling, the ferromagnetic core is found to be unconditionally stable in the bias direction.


Get permission to re-use this article. Mryasov 3R. However, with decreasing particle size the magnetic anisotropy energy per particle responsible for holding the magnetic moment along certain directions becomes comparable to the thermal energy.

Evans 1R.

Beating the superparamagnetic limit with exchange bias.

In order to permit magnetic recording, which essentially requires a bi-stable system, we propose a heat-assisted recording method, whereby both the ferromagnet FM and antiferromagnet AF are switched.

Our results show that exchange-biased systems exhibit an increased energy barrier along the bias direction, with a corresponding decrease of the barrier in the opposite direction. The Institute of Physics IOP is a leading scientific society promoting physics and bringing physicists together for the benefit of all. The European Physical Society EPS is a not for profit association whose members include 41 National Physical Societies in Europe, individuals from all fields of physics, and European research institutions.

Chantrell 1 and O.

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