Magnetization can surf on the top of a laser-induced sound wave

Apr 11, 2014
Magnetization can surf on the Top of a Laser-Induced Sound Wave
Artistic representation of sound waves triggered in a medium with the help of a femtosecond laser pulse. The sound wave at the frequency f causes a very anharmonic response of the magnetization that oscillates at the frequencies f, 2f and 3f. Credit: D. Afanasiev

An effective coupling between magnetism and light can be mediated by sound. This newly discovered phenomenon could be important for recording data on a magnetic device with the help of light. Physical Review Letters publishes the finding of a team from Radboud University (Netherlands) and Taurida National University (Crimea) in their issue of April 11.

Controlling the of media with the help of light may be the best way to develop a new generation of magnetic data storing devices. The problem, however, is to find an effective mechanism for optically controlling magnetism. Indeed, according to quantum mechanics the strongest effect in light-matter interaction is the effect of the electric field of light on the electrons, suggesting that some net magnetization must be conserved.

An international team of scientists from Nijmegen (the Netherlands) and Simferopol (Crimea) has discovered a very effective method of optically controlling magnetism: an intense and ultrashort (shorter than 100 femtoseconds) laser pulse excites electrons in a medium to such an extent, that the excited electron-clouds push the atoms off, thereby bringing them in motion and launching a sound wave.

The fact that the can effectively couple to the magnetization is well known. Unexpectedly, the scientists found that the optically launched sound at the frequency f is accompanied by a response of the magnetization at the frequencies f, 2f and 3f. Such a phenomenon is called anharmonicity. Any pendulum becomes anharmonic if the deviations from the equilibrium become large.

"The fact that the laser-induced oscillations of the magnetization are anharmonic is very intriguing. It means that the coupling of light with the magnetism is very effective and we are getting close to our dream – to record magnetic information with the help of " says Alexey Kimel, Associate Professor and research group leader at Radboud University, the Netherlands.

It is remarkable that the scientists observed this effect in iron borate. This material is very similar to hematite – one of the cheapest magnets and widely spread minerals. "For optical experiments green iron borate is much more convenient than black hematite, while the phenomena in those crystals are very similar."

Explore further: Semiconductor material can be magnetized with light, suggesting new technology opportunities

More information: "Laser Excitation of Lattice-Driven Anharmonic Magnetization Dynamics in Dielectric FeBO3." D. Afanasiev, I. Razdolski, K. M. Skibinsky, D. Bolotin, S. V. Yagupov, M. B. Strugatsky, A. Kirilyuk, Th. Rasing, and A. V. Kimel. Phys. Rev. Lett. 112, 147403 – Published 9 April 2014. journals.aps.org/prl/abstract/… ysRevLett.112.147403

add to favorites email to friend print save as pdf

Related Stories

Controlling magnetism with an electric field

Feb 18, 2014

There is a big effort in industry to produce electrical devices with more and faster memory and logic. Magnetic memory elements, such as in a hard drive, and in the future in what is called MRAM (magnetic random access memory), ...

Magnetic switch gets closer to application

Jan 27, 2014

Scientists from Paris, Newcastle and Helmholtz-Zentrum Berlin have been able to switch on and off robust ferromagnetism close to room temperature by using low electric fields. Their results are inspiring ...

Recommended for you

What time is it in the universe?

Aug 29, 2014

Flavor Flav knows what time it is. At least he does for Flavor Flav. Even with all his moving and accelerating, with the planet, the solar system, getting on planes, taking elevators, and perhaps even some ...

Watching the structure of glass under pressure

Aug 28, 2014

Glass has many applications that call for different properties, such as resistance to thermal shock or to chemically harsh environments. Glassmakers commonly use additives such as boron oxide to tweak these ...

Inter-dependent networks stress test

Aug 28, 2014

Energy production systems are good examples of complex systems. Their infrastructure equipment requires ancillary sub-systems structured like a network—including water for cooling, transport to supply fuel, and ICT systems ...

Explainer: How does our sun shine?

Aug 28, 2014

What makes our sun shine has been a mystery for most of human history. Given our sun is a star and stars are suns, explaining the source of the sun's energy would help us understand why stars shine. ...

User comments : 0