Nature Physics - A study on the interaction between chirality and magnetism

 
With an interdisciplinary study crossing chemistry and physic combination of interesting phenomena has been explored. Magneto-chiral dichroism is a non-reciprocal—that is, directional— effect observed that can be  observed in magnetized chiral systems, featuring an unbalanced absorption of unpolarized light depending on the direction of the magnetization. Despite the fundamental interest in a phenomenon breaking both parity and time-reversal symmetries, magneto-chiral dichroism is one of the least investigated aspects of light–matter interaction most likely because of the weakness of the effect in most reported experiments. 
 
The teams were able to exploited the element selectivity of hard X-ray radiation to investigate the magneto-chiral properties of enantiopure crystals of two isostructural molecular helicoidal chains comprising either cobalt(II) or manganese(II) ions. A strong magnetochiral dichroism, with Kuhn asymmetry of the order of a few per cent, has been observed in the cobalt chains system, whereas it is practically absent for the manganese derivative. The spectral features of the X-ray magneto-chiral dichroism signal differ significantly from the natural and magnetic dichroic contributions and have been rationalized by the authors by using the multipolar expansion of matter–radiation interaction.

R. Sessoli, M.-E. Boulon, A. Caneschi, M. Mannini, L. Poggini, F. Wilhelm, A. Rogalev, Strong magneto-chiral dichroism in a paramagnetic molecular helix observed by hard X-ray, http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys3152.html, doi:10.1038/NPHYS3152

In the same issue of Nature Physics and interesting News & Views, introducing the magnetic dichroism was presented by Jose Ramon Galan-Mascaros. He describes and explain how the magnetic fields can be used to modify light absorption in chiral media, reminding that the effect is weak, so the potential of this approach has gone largely untapped until the moment that it was possible to access to synchrotron radiation. He also describe the main goals of the following paper by Sessoli et al. showing how the power of that radiation may provide a solution, enabling surprisingly strong dichroisms in a molecular helix.

Jose Ramon Galan-Mascaros, Magneto-chiral dichroism: Bring to light
http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys3200.html, doi:10.1038/nphys3200,
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