Multistate per-cell magnetoresistive random-access memory written at curie point

Y. K. Zheng*, Y. H. Wu, Zaibing Guo, G. C. Han, K. B. Li, J. J. Qiu, H. Xie, P. Luo

*Corresponding author for this work

    Research output: Contribution to journalConference articlepeer-review

    12 Scopus citations


    A multistate per-cell magnetoresistive random-access memory (MRAM) that writes data by a thermally assisted technique and reads data using the angular-dependent magnetoresistance is proposed. A hard magnetic layer or pinned ferromagnetic layer (CoFe-IrMn) is used as the recording layer. The free layer serves as the read layer. Before reading, the free layer's magnetization is set to the initial state. For the N states per-cell MRAM, the magnetization angle of the ith state (i = 0 to N - 1) between the free layer and recording layer can be set to be ac os (1 - 2*i/(N - 1)). For example, in the four-state per-cell MRAM, the magnetization angle can be set to be acos(1), acos(1/3), acos(-1/3), and acos(-1), which represent the four states, respectively. More states can be obtained if the signal-to-noise ratio is sufficient. At near Curie point, a small external field can be used to record the signal. In order to verify the idea, a spin-valve giant-magnetoresistance memory cell was fabricated using e-beam lithography and ultrahigh voltage sputtering. A 25-mA heating current and a small external field are enough to assistant the writing process. A four-state per-cell memory is realized by this method.

    Original languageEnglish (US)
    Pages (from-to)2850-2852
    Number of pages3
    JournalIEEE Transactions on Magnetics
    Issue number5 I
    StatePublished - Sep 1 2002
    Event2002 International Magnetics Conference (Intermag 2002) - Amsterdam, Netherlands
    Duration: Apr 28 2002May 2 2002


    • Giant magnetoresistance
    • Magnetic tunnel junctions
    • Magnetoresistive random-access memory
    • Spin valves
    • Thermal-assistant writing

    ASJC Scopus subject areas

    • Electronic, Optical and Magnetic Materials
    • Electrical and Electronic Engineering


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