Researchers at the RIKEN Advanced Science Institute at Wako, Japan have discovered a magnet that becomes weaker as the number of electrons increases. In other words, a magnet can be stable without excess electrons, signifying the presence of an energy-dissipation-free electrical mode suitable for low power electronic applications. Powerful magnets do not need an abundance of electrons, which makes them more energy efficient.
The new magnet is comprised of bismuth telluride and manganese and is part of a newly discovered class of magnetic material known as topological insulators.
Electronic applications are able to use this new magnetic material because the surface electrons do not scatter easily and electrons on the surface occupy a special state known as the Dirac cone. The electrons surrounding the tip of the Dirac cone create the material’s magnetic properties.
However, there are limitations. Only a small number of electrons can be on the surface state, so, as electrons are pumped into the system, the crucial electronic states are filled and magnetism is weakened. A careful balance must be struck between too many and too few electrons in order to create the perfect magnet.
The critical temperature above which magnetism disappears is higher than for the case of a higher number of injected electrons in low electron densities. Magnetism even disappears above a certain threshold.