Researchers develop magnetic nanoswitch for thermoelectric voltages

A team from Physikalisch-Technische Bundesanstalt (PTB) in Germany has devised a way to use the heat that occurs in tiny computer processors to switch them more easily or to store data more efficiently. The 'thermoelectric voltage' has the potential to be used in nanojunctions, small components based on magnetic tunnel structures. Magnetic tunnel structures occur in IT applications such as magnetic storage cells in non volatile magnetic memory chips or as highly sensitive magnetic sensors to read out the data stored on hard disks. According to PTB, the new effect could enable monitoring and controlling of thermoelectric voltages and currents in highly integrated electronic circuits. Magnetic tunnel structures consist of two magnetic layers separated by a thin insulation layer of approximately 1nm. The magnetic orientation of the two layers inside the tunnel structure has a great influence on its electrical properties. If the magnetic moments of the two layers are parallel to each other, the resistance is low; ifthey are opposed to each other, the resistance is high. The change in the resistance when switching the magnetisation can amount to more than 100% so it's possible to control the electric current flowing through the magnetic tunnel structure by simply switching the magnetisation. The work carried out by the PTB researchers now shows that, besides the electric current, the thermal current flowing through the tunnel structure can also be influenced by switching the magnetisation. In experiments, scientists generated a temperature difference between the two magnetic layers and investigated the electric voltage generated. It turned out that the thermoelectric voltage depends on the magnetic orientation of the two layers nearly as strongly as the electric resistance. By switching the magnetisation, it is therefore possible to control the thermoelectric voltage and, ultimately, the thermal current flowing through the specimen. In future, the new effect could be applied by using and converting the energy of waste heat occurring in integrated circuits in a targeted way. The results obtained by the researchers have been published in Physical Review Letters.