New nanoscale cooling element works in electrical insulators as well

Researchers led by University of Groningen physcis professor Bart van Wees have designed a miniscule cooling element that uses spin waves to transport heat in electrical insulators. The cooling element could be used to dissipate heat in the increasingly smaller electrical components of computer chips.

The researchers from NWO's FOM Foundation, the University of Groningen, Delft University of Technology and Tohoku University in Japan published their design online on 7 July 2014 in Physical Review Letters, FOM Foundation reports.

The functioning of the cooling element is based on the spin of the electrons. Spin is a fundamental property of an electron that corresponds with its magnetic moment (the strength and direction of its magnetic field). Although physicists have used spin for cooling purposes before, this is the first time that they have successfully done this in insulating materials.

The researchers used a 200-nanometre thick insulator of yttrium-iron garnet (a mineral) with a 20 by 200 micrometre layer of platinum on top. Electrons can easily flow through the conducting platinum but when they reach the insulating garnet they cannot go any further. Nevertheless, the spin of the electrons is transferred: the magnetic moment of the electron influences the magnetic moment (and therefore the spin) of the electrons in the insulator that are at the boundary between the two materials.

Through magnetic coupling this spin change is subsequently transferred to electrons that are situated further away from the boundary. In this manner a wave of spin changes appears to proceed through the material. The spin wave also transfers heat to or from the boundary. Dependent on the direction of both the spin and the magnetisation in the mineral, the boundary will therefore cool down or heat up.

See for more information the full FOM press release