Magnétisme et chiralité

News: Chirality is the property of objects, and particularly of molecules, to exist in two different forms that are each other’s mirror image. Chirality plays a vital role in biochemistry, as most molecules of life, ranging from sugars and proteins, via most drugs, right up to DNA, are chiral and this property is essential for their action. Magnetism, despite its millennia-long history, still fascinates. It has found many industrial applications, and new ones are still being developed, spintronics being its most recent offspring. Since Pasteur, scientists have tried to create a link between chirality and magnetism. Although basically very distinct, the two domains share a common and unique phenomenon called magneto-chiral anisotropy (MChA). MChA corresponds to a change in any flux (light, electrical current, heat, sound, etc.) going through a chiral medium, depending on whether it flows parallel or anti-parallel to an external magnetic field. The first predictions of MChA for light appeared in the 1980s. Since then several observations of optical MChA have been reported, but the effects were quite weak and no complete quantitative analysis was presented.  Now a collaboration of researchers from France and the USA have performed detailed measurements and advanced quantum-chemical calculations on well-defined model systems. They find experimentally that for these materials at low temperatures, the difference in light transmission parallel and anti-parallel to a modest magnetic field of 1 Tesla, hardly more than what a refrigerator magnet produces, can be as high as 10 %. Their calculations permit a detailed understanding of these results, and predict even higher anisotropies at higher fields or lower temperatures. The size of the effect and its in-depth understanding now open the road to applications of MChA, which can range from optical diodes to new optical data storage methods. (read also in french, Communication by INP-CNRS)
Laboratory : ICMCB