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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Chantrell 1 and O. To find out more, see our Privacy and Cookies policy. Such a system is ideal for thermal stability since there is no energetically stable reversed state, providing the antiferromagnetic shell is unchanged.

Beating the superparamagnetic limit with exchange bias.

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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. Get permission to re-use this article.


Evans 1R. By continuing to use this site you agree to our use beatibg cookies.

For systems with large values of the interfacial coupling, the ferromagnetic core is found to be unconditionally stable in the bias direction. Sign up for new issue notifications. Mryasov 3R. As a thee society, the EPS engages in activities that strengthen ties among the physicists in Europe.

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.

Evans et al EPL 88 Interest in magnetic nanoparticles has increased biae the past few years by virtue of their potential for applications in fields such as ultrahigh-density recording and medicine.

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.

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.

Here we show that magnetic exchange coupling induced at the exchznge between ferromagnetic and antiferromagnetic systems can provide an extra source of anisotropy, leading to magnetization stability. 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.


It works to advance physics research, application and education; and engages with policy makers and the public to develop awareness and understanding of physics. 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.

Yanes 2O. This site uses cookies.

On beating the superparamagnetic limit with exchange bias

This behaviour is ascribed to the specific way ferromagnetic nanoparticles couple to an antiferromagnetic matrix. 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. Thus, the demand for further miniaturization comes into conflict with the superparamagnetism caused by the reduction of the anisotropy energy per particle: Most applications rely on the magnetic order of the nanoparticles being stable with time.

In order to investigate the possibility of “beating the superparamagnetic limit with exchange bias” Skumryev V.