Synthetic ferrimagnet promises energy efficienct thermally induced switching
The development focuses on all-optical thermally induced magnetic switching (TIMS), which uses ultrafast laser pulses to change the magnetic state of the material, equivalent to writing a single bit of data. In all-optical switching there is no need to use magnetic fields to write the data and so a significant reduction in power consumption can be made. The deposited laser energy per written bit is much smaller.
Magnetic materials are currently used to store almost all digital information. Information processing and storage now represents a significant fraction of the world’s energy consumption and continuing improvements in energy efficiency will require the development of new technologies and materials.
To date, only rare-earth-transition-metal alloys called ferrimagnets have been shown to exhibit all-optical switching. However, these materials are both difficult to produce at the nanoscale necessary for technological devices and are expensive because they use rare-earth metals such as Gadolinium (Gd) and Terbium (Tb).
The research, led by York’s Department of Physics and involving scientists from Helmholtz-Zentrum Berlin (HZB), Germany and Radboud University Nijmegen, the Netherlands, demonstrates the use of a synthetic ferrimagnet – a sandwich of two ferromagnetic materials and a non-magnetic spacer layer. The spacer layer engineers the coupling between the two ferromagnets so that they align opposite to one another. When subjected to an ultrafast laser pulse this structure spontaneously switches its magnetic state representing writing a single bit of data.
Corresponding author Dr Richard Evans, from York’s Department of Physics, explained: "Energy efficiency is one of the most important goals for technological devices due to their expanding use with an increasing world population and resultant demand for energy. The synthetic ferrimagnet structure overcomes the intrinsic problems of rare-earth-transition-metal alloys and paves the way for a new class of magnetic materials and devices with improved performance and power efficiency. The results are a significant step towards realising a device based on thermally induced switching as it shows that structures on the nanometer length scale can be used."
The research received financial support from the EU Seventh Framework Programme, as well as the Netherlands Organization for Scientific Research (NWO) and the Foundation for Fundamental Research on Matter (FOM).
Reference: ‘Ultrafast thermally induced magnetic switching in synthetic ferrimagnets’ is published in Applied Physics Letters at https://scitation.aip.org/content/aip/journal/apl/104/8/10.1063/1.4867015
Authors: Richard F. L. Evans, Thomas A. Ostler, Roy W. Chantrell, Ilie Radu and Theo Rasing.
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