Sample cryostat of the LEM apparatus.
Superconductors, materials that carry electrical current without generating any heat, and magnets are usually incompatible. Researchers were thus surprised when they recently observed that under certain conditions superconductivity actually promotes magnetization in an adjacent normal metal. The results were published in Nature Physics.
Future supercomputers can become more energy-efficient if advances are made in the field of spintronics. However the electron spins are very difficult to control, making it difficult to develop superconducting spintronics devices.
Now an international team of scientists from the UK, Russia and Switzerland, investigated the relation between superconductivity and magnetization in order to understand how to control electron magnetic moments. They used superconducting spin valves, which consisted of two ferromagnetic cobalt layers, one superconducting niobium layer, and a layer of gold. Thanks to muon experiments at the Paul Scherrer Institute (PSI) in Switzerland they could observe how the magnetization proceeds in different layers of the sample. This could be achieved by implanting the muons in the different layers and using the muons’ spins as microscopic magnetometers.
The Low-Energy Muon Facility (LEM) at PSI used for the experiment.
When magnetization directions in two ferromagnetic layers were not parallel, the interaction between these layers and the superconductive layer induced magnetization in the uppermost gold layer. This indicated that the information of the relative alignment of the magnetic layers could be transferred over long distances through the superconducting layer. When the team changed the magnetization directions in two magnetic layers, making them parallel, the effect almost disappeared, the field intensity decreasing by 20-fold.
These observations show that superconductivity can promote magnetization and thus control the electron spin. This paves the way to future energy-efficient supercomputers.
M. G. Flokstra, N. Satchell, J. Kim, G. Burnell, P. J. Curran, S. J. Bending, J. F. K. Cooper, C. J. Kinane, S. Langridge, A. Isidori, N. Pugach, M. Eschrig, H. Luetkens, A. Suter, T. Prokscha & S. L. Lee, Remotely induced magnetism in a normal metal using a superconducting spin-valve, Nature Physics (2015) DOI: 10.1038/nphys3486
Text prepared with materials from Phys.org, a press release from the University of St Andrews and Lomonosov Moscow State University.
_M. G. Flokstra and S. L. Lee rom the University of St Andrews in the UK have received NMI3 support to conduct experiments at PSI in Switzerland. The experiments were supported through the NMI3 Access Programme