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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Beating the superparamagnetic limit with exchange bias.

Get permission to re-use this article. Thus, the demand for further miniaturization comes into conflict with the superparamagnetism caused by the reduction of the anisotropy energy per particle: 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.

Mryasov 3R. To find out more, see our Privacy and Cookies policy. As a federation of National Physical Societies, the EPS studies issues of concern to all European countries relating to physics research, science policy and education. This site uses cookies.

Most applications rely on the magnetic order of the nanoparticles being stable with time. 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.


Chantrell 1 and O. Evans 1R.

On beating the superparamagnetic limit with exchange bias

For systems with large values of the interfacial coupling, the ferromagnetic core is found to be unconditionally stable in the bias direction. It works to advance physics research, application and education; and engages with policy makers and the public to develop awareness and understanding of physics. It has a worldwide membership of around 50 comprising physicists from all sectors, as well as those with an interest in physics. As a learned society, the EPS engages in superpafamagnetic that strengthen ties among the physicists in Europe.

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Beating the superparamagnetic limit with exchange bias.

In order to exdhange 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.

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In order to investigate the possibility of “beating the superparamagnetic limit with exchange bias” Skumryev V. 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. This behaviour is ascribed to thr specific way ferromagnetic nanoparticles couple to an antiferromagnetic matrix.

Evans et al EPL 88 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. We demonstrate this principle for ferromagnetic cobalt nanoparticles of about 4 nm in diameter that are embedded in either a paramagnetic or an antiferromagnetic matrix.


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. 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. The Institute of Physics IOP is a leading scientific society promoting physics and bringing physicists together for the benefit of all.

Yanes 2O.

Beating the superparamagnetic limit with exchange bias – Dimensions

The European Physical Society EPS is a not for profit association whose members include 41 National Physical Societies in Europe, wwith from all fields of physics, and European research institutions. Such a system is ideal for thermal stability since there is no energetically stable reversed state, providing the antiferromagnetic shell is unchanged.

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