Strong magneto-chiral dichroism in enantiopure chiral ferromagnets

• Published in: Nature materials Vol. 7; no. 9; pp. 729 - 734
• Main Authors: Train, Cyrille, Gruselle, Michel, Gheorghe, Ruxandra, Krstic, Vojislav, Chamoreau, Lise-Marie, Ovanesyan, Nikolai S, Rikken, Geert L. J. A, Verdaguer, Michel
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.09.2008; Nature Publishing Group
• Subjects: Ammonium; Asymmetry; Biomaterials; Chemical engineering; Chemical synthesis; Chemistry and Materials Science; Chromium; Condensed Matter; Condensed Matter Physics; Curie temperature; Dichroism; Ferromagnetism; Ions; Magnetism; Magnetization; Manganese; Materials Science; Nanotechnology; Optical and Electronic Materials; Oxalates; Physical properties; Physics; Self assembly; Superconductivity; Synthesis
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/nmat2256

As materials science is moving towards the synthesis, the study and the processing of new materials exhibiting well-defined and complex functions, the synthesis of new multifunctional materials is one of the important challenges. One of these complex physical properties is magneto-chiral dichroism which arises, at second order, from the coexistence of spatial asymmetry and magnetization in a material. Herein we report the first measurement of strong magneto-chiral dichroism in an enantiopure chiral ferromagnet. The ab initio synthesis of the enantiopure chiral ferromagnet is based on an enantioselective self-assembly, where a resolved chiral quaternary ammonium cation imposes the absolute configurations of the metal centres within chromium–manganese two-dimensional oxalate layers. The ferromagnetic interaction between Cr( III ) and Mn( II ) ions leads to a Curie temperature of 7 K. The magneto-chiral dichroic effect is enhanced by a factor of 17 when entering into the ferromagnetic phase. Magneto-chiral dichroism is an effect in which unpolarized light is absorbed differently for parallel and antiparallel propagation with respect to an applied magnetic field. Previous observations have only seen a rather weak demonstration of this effect. Following a challenging synthesis, strong magneto-dichroism has now been observed in enantiopure chiral ferromagnets.