Spin-transfer in nanopillars with a perpendicularly magnetized spin polarizer

J. M.L. Beaujoura, D. B. Bedaua, H. Liua, M. R. Rogosky, A. D. Kenta

    Research output: Chapter in Book/Report/Conference proceedingConference contribution


    Spin-transfer devices that incorporate a polarizer with its magnetization orthogonal to a switchable (free) layer offer the potential for ultra-fast switching, low power consumption and reliable operation. The non-collinear magnetizations lead to large initial spin-transfer torques, eliminating the incubation delay seen in devices with collinear magnetization. Here we present the basic electrical and magnetic characteristics of spin-valve nanopillars that incorporate a perpendicularly magnetized polarizer and demonstrate current-induced switching with short current pulses, down to 100 ps in duration. We have fabricated devices that have a CoNi polarizer with perpendicular magnetization and an in-plane magnetized 3 nm thick Co free layer and a 12 nm thick Co reference layer, each separated by thin (̃ 10 nm) Cu layers. The magnetization of the reference layer is collinear with that of free layer to read out the device state. The reference layer also contributes to the spin-accumulation acting on the free layer and leads to a spin-torque that favors the parallel (P) or antiparallel (AP) state depending on the current pulse polarity, reducing the requirement of precise pulse timing in precessional reversal. The anisotropy field of the perpendicular polarizer is 1.3 T, i.e. it is high enough so that in-plane fields (< 0.3 T) applied to switch the magnetizations of the reference and free layers do not reorient the polarizer. Our typical nanopillar device lateral dimensions are between 60 nm and 300 nm and nanopillars are positioned on coplanar waveguides to allow for broadband electrical connections and studies with fast rise time pulses, generated by an arbitrary waveform generator. The switching probability has been determined for variable pulse amplitude and duration, from 0.1 to 10 ns at room temperature.

    Original languageEnglish (US)
    Title of host publicationSpintronics II
    StatePublished - 2009
    EventSpintronics II - San Diego, CA, United States
    Duration: Aug 2 2009Aug 5 2009

    Publication series

    NameProceedings of SPIE - The International Society for Optical Engineering
    ISSN (Print)0277-786X


    OtherSpintronics II
    Country/TerritoryUnited States
    CitySan Diego, CA


    • Magnetic random access memory
    • OST-MRAM
    • Orthogonal spin transfer MRAM
    • Perpendicular magnetization
    • Spin transfer

    ASJC Scopus subject areas

    • Electronic, Optical and Magnetic Materials
    • Condensed Matter Physics
    • Computer Science Applications
    • Applied Mathematics
    • Electrical and Electronic Engineering


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