有机分子可稳定材料磁性

Organic molecules² allow producing printable electronics and solar cells with extraordinary properties. In spintronics, too, molecules open up the unexpected possibility of controlling the magnetism³ of materials and, thus, the spin of the flowing electrons. According to what is reported in Nature Materials by a German-French team of researchers, a thin layer of organic molecules can stabilize⁴ the magnetic orientation⁵ of a cobalt surface. (DOI: 10.1038/NMAT4361) "This special interaction between organic molecules and metal surfaces could help to manufacture information storage systems in a more simple, flexible and cheaper way," explains Wulf Wulfhekel from KIT⁶. Microscopic⁷ magnets with constant orientation are used in hard disks, for example. With a view to "printable electronics", organic molecules indeed could open up new simple production methods utilizing⁸ the self-organization of molecules.

 

In the present study, three molecular⁹ layers of the dye phtalocynine were applied¹⁰ to the surface of ferromagnetic¹¹ cobalt. Whereas the magnetic moments of the molecules alternatingly align¹² relative to the cobalt and relative to each other, the molecules form a so-called antiferromagnetic arrangement. The magnetic orientation of this combination of antiferromagnetic and ferromagnetic materials remains¹³ relatively¹⁴ stable even in the presence of external magnetic fields or cooling. "Surprisingly, the "lightweight" molecule¹ wins this magnetic arm wrestling with the "heavyweight" ferromagnetic material and determines the respective properties," Wulfhekel says. Systems of antiferromagnetic and ferromagnetic materials, among others, are used in hard disk reading heads. So far, manufacturing of antiferromagnets has been quite complex and time-consuming. Should molecules be suitable for use in the production, the antiferromagnets one day will simply come out of the printer.

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