The scientists investigated what happens in a device where a very thin layer of a superconductor, a material that carries electrical current without generating any heat, is sandwiched between a layer of a magnetic material and a layer of gold.
Magnetic gold
They discovered that under certain conditions the layer of gold becomes magnetic due to charge carriers flowing out of the superconductor into the metal.
The ability to generate and to manipulate magnetic currents in this way has the potential for applications in new types of electronic devices in future. The research is published on the Nature Physics website.
The experiments involved a large team of collaborators led by Professor Steve Lee of the University of St Andrews, including the University of Bath, the University of Leeds, Royal Holloway and Bedford College (University of London), the ISIS Facility and the Paul Scherrer Institute in Switzerland.
Spintronics
Dr Machiel Flokstra, of the School of Physics and Astronomy at St Andrews, who led the experiment said:
“Superconductors are materials that, if cooled sufficiently, lose their resistance, that is, they carry electricity without dissipating heat.
“This is possible because the electrons that carry the electrical charge bind together into pairs that are able to move without losing energy. Each electron is itself like a tiny bar magnet, since these charged electrons spin about their own axes.
“When they form into superconducting pairs these electronic `spins’ align oppositely, so that the magnetic fields cancel out. It transpires that in these new devices these pairs of electrons can be separated into two currents moving in opposite directions, one with magnetic fields (spins) pointing up and one with them pointing down.
“The idea of generating `spin currents’ is the basis of the emerging field of spintronics. In conventional electronics only electrical charges can be manipulated, but it is hoped in the field of spintronics that electron spins can also be controlled, leading to novel advanced electronic devices.”
Faster, smaller electronics
Researchers in Professor Simon Bending’s group in the Department of Physics have been using a unique low temperature scanning probe microscope to systematically study magnetisation reversal in these superconducting spin-valve samples and eliminate alternative origins for the remotely-induced magnetisation observed.
Professor Bending, Head of the Department of Physics at the University of Bath, said: "This is a really ground-breaking piece of research whose long-term goal is to marry the fields of spintronics and superconductivity.
"We believe that for the first time we have observed spin accumulation arising from a current of spin-carrying pairs of superconducting electrons that can be controlled by manipulating the magnetisation direction in a ferromagnetic control electrode.
"This is the first step to realising superconducting spintronic devices that operate without generating heat and could be the basis for entirely new types of computers that are faster, smaller and more powerful than before."