Nano wires become magnetic

Carbon brings magnetism into the electronics

Images of manganese silicide with carbon ions implanted through a gold mask. The squares are 7 x 7 square microns in size. © American Institute of Physics
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A few years ago, Japanese researchers randomly made a compound of silicon, manganese, and carbon that was unexpectedly ferromagnetic at room temperature. German researchers have now succeeded in producing magnetic "nano-wires" made of this material.

As the scientists from Karlsruhe and Dresden report in the journal "Applied Physics Letters", they implanted carbon ions at elevated temperature in manganese silicide for this purpose.

Silicon is the most important material for the production of mobile phone or computer chips. New magnetic properties of silicon compounds therefore always evoke a great deal of echo.

Christoph Sürgers from the University of Karlsruhe and Kay Potzger from the Research Center Dresden-Rossendorf (FZD) deal with the interaction of magnetic and electronic properties of materials. Each electron is like a tiny magnet, because it has its own spin, the spin. Since the spin has at least two different setting options, its use as an information carrier (on / off or 0/1) offers itself.

Hard drives with huge storage capacity

As early as the 1980s, the 2007 Nobel Prize for Physics, Grünberg and Fert, discovered the giant magnetoresistance (Giant Magnetoresistance (GMR)), which enables hard disks with a storage capacity of many gigabytes. Thus they justified the promising spin electronics or spintronics. However, reducing the size of the tracks to the nanometer scale (one nanometer equals one millionth of a millimeter) could also produce completely new effects, and even lead to more stable circuits. display

These approaches have now been successfully combined in the ion beam center of the FZD on the basis of materials from Karlsruhe. Potzger implanted carbon ions into a thin layer of manganese silicide (Mn5Si3). To be able to better investigate the new composite material, he then decided to implant the carbon ions into small square surfaces for the first time using a shadow mask.

A "trap" for carbon

However, at the substrate temperatures of about 450 ° C used during implantation, the carbon migrates from the center of the squares to the edges where it forms regular ferromagnetic nanowires of manganese, silicon, and carbon.

In the nano-wires, the magnetic moments generated by the electrons are aligned parallel to each other. This state is ideally suited for further work devoted to the transport of electrons in nano-wires. The researchers want to generate specific defects in thin layers of material, which should serve as "trap" for the implanted carbon.

(idw - Research Center Dresden - Rossendorf, 21.08.2008 - DLO)