New way of propelling magnetic nanobits forwards
Researchers from Eindhoven University of Technology (TU/e) and the FOM Foundation have succeeded in enabling magnetic bits to move in an alternative manner through nanowires by using the so-called Spin Hall Effect. This is vitally important for the development of the race track memory. The results of the research were published last Sunday (3 February) online in the top journal Nature Materials. Interestingly the first author is a graduating student.
The racetrack memory is a highly promising new technology for data storage that is necessary because the development of the standard electrical memory chips is reaching its limits. This is because each bit in a normal memory chip is linked to a relatively large and expensive transistor. The racetrack memory has therefore been devised in which far more data can be stored than in the current chips. In this memory the magnetic bits – ultrasmall areas with a different magnetisation – move backwards and forwards through a nanowire past the reading and writing head. None of the parts move, only the data, so the system is very energy efficient.
Up until now the bits were propelled by applying an electric current to the magnetic layer containing the nanobits. The Eindhoven researchers, however, have done this indirectly: via a spin current applied to the neighbouring layer a so-called 'Spin Hall Effect' arises that propels the nanobits in the magnetic layer. That the propelling effect originates in a non-magnetic nano-layer is a very surprising result.
The researchers made magnetic nanowires with the help of concentrated ion beams. Various nanobits are found in these wires which can subsequently be moved by an electric current. The striking behaviour of the bits could only be explained by the Spin Hall Effect. The researchers can carefully manipulate this behaviour.
"This research not only contributes to a better understanding of the Spin Hall Effect, but will also yield new nano-electronics in which magnetic information at the nanometre scale can be stored and read out in a unique manner," says TU/e professor Henk Swagten (Physics of Nanostructures Group) about the research.
The publication in Nature Materials is very special for another reason: it is the result of work by a graduating student, Pascal Haazen, who was the first author. Swagten: "Pascal has put forward the ideas, carried out all of the experiments, interpreted the results and performed the modelling. He subsequently wrote the paper for Nature Materials, including the subsequent discussion with the referees. That is most unusual and something I have never previously experienced with a graduating student." Haazen graduated last year with absolute top marks which is unique for the group concerned.
The article 'Domain wall depinning governed by the spin Hall' was published on 3 February in Nature Materials, DOI 10.1038/NMAT3553. The authors are P.P.J. Haazen, E. Murè, J.H. Franken, R. Lavrijsen, H.J.M. Swagten and B. Koopmans, all from Eindhoven University of Technology. The research received financial support from the FOM Foundation.
For further information please contact Pascal Haazen or Henk Swagten. You can also contact the science communication officer Ivo Jongsma +31 (0) 40 247 21 10.