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Researchers study thermoelectric voltage effect

Posted: 02 Nov 2011     Print Version  Bookmark and Share

Keywords:magnetic tunnel structure  thermoelectric voltage  waste heat 

Now waste heat from small processors can be controlled through magnetisation, according to researchers at the Physikalisch-Technische Bundesanstalt (PTB) who noticed that thermoelectric voltage effect in magnetic tunnel structures can be used in nano-electronic junctions.

The discovery may mean that the heat that occurs in MPUs might soon no longer be a problem. On the contrary it may be used to switch the processors more easily or to store data more efficiently. Its application would include monitoring and controlling thermoelectric voltages and currents in highly integrated electronic circuits.

Magnetic tunnel structures consist of two magnetic layers separated only by a thin insulation layer of about 1nm—the so-called 'tunnel barrier.' 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. If they are opposed to each other, the resistance is high. The change in the resistance when switching the magnetisation can amount to more than 100 per cent. It is therefore possible to control the electric current flowing through the magnetic tunnel structure efficiently by simply switching the magnetisation.

The work carried out by the PTB researchers show that, besides the electric current, the thermal current flowing through the tunnel structure can be influenced by switching the magnetisation. In their experiments, the scientists generated a temperature difference between the two magnetic layers and investigated the electric voltage generated. 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, also the thermal current flowing through the specimen.

In the future, this new effect could be applied, for example, by using and converting the energy of waste heat occurring in ICs in a targeted way. Furthermore, the discovery of this so-called 'tunnel magneto thermoelectric voltage' claims to be a milestone in the research field 'spin calorics.'

- Paul Buckley
  EE Times

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