Airy magnets

Spanish researchers have created a new type of magnetic material that is ultra-light and transparent. The airy magnets could have applications in flat screen displays and magneto-optical memory devices for computers.

Elies Molins of The Barcelona Science and Materials Institute (ICMAB) and colleagues at the Physics Department, the Autònoma University of Barcelona (UAB), and the University of Zaragoza combined an extremely light form of silica known as an aerogel, a kind of solid foam that is 95% air, with extremely fine magnetic particles composed of neodymium, iron, and boron (Nd₂Fe₁₄B); an iron-based rare-earth magnetic material discovered in 1983. A magnetic field applied during the synthesis process ensures the magnetic particles are aligned.

	showing (a) unaligned opaque aerogel, (b) aligned in a magnetic field and transparent.

The material, being a mixture rather than a compound, retains the transparent and lightweight properties of the aerogel, as well as the magnetic properties of the magnetic particles. The new materials have a distinct advantage over other lightweight magnetic composites in that they are not affected by weak external magnetic fields and so could ultimately be used for information storage where others have failed. Transparency means magneto-optical memory devices that can be read with a laser might be possible. But, the materials are anisotropic, so are opaque when viewed at ninety degrees to their transparent view, which means they could be used as magnetically switchable pixels in a flat display.

Aerogels have some unusual properties including their strange timbres Click image to see movie

The extremely light and porous composition of the magnetic aerogels also endows them with the lowest levels of thermal, electrical, and sound conductivity in this class of materials, which means it could also be used in non-conducting magnetic components. X-ray diffraction, ⁵⁷Fe Mössbauer and UV-Vis spectroscopies, and SQUID magnetometry were used to reveal the structural and magnetic properties of the new materials.

"Of course, applications are too far to be reached in a short time," Molins told Reactive Reports, "but open a window to jump from the current 2D world in microelectronics and information storage to the 3D one."

Appl. Phys. Lett., 2003, 82, 4307-4309; http://dx.doi.org/10.1063/1.1578538