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Title: Multistate per-cell magnetoresistive random-access memory written at curie point
Authors: Zheng, Y.K.
Wu, Y.H. 
Guo, Z.B.
Han, G.C.
Li, K.B.
Qiu, J.J.
Xie, H.
Luo, P.
Keywords: Giant magnetoresistance
Magnetic tunnel junctions
Magnetoresistive random-access memory
Spin valves
Thermal-assistant writing
Issue Date: Sep-2002
Citation: Zheng, Y.K., Wu, Y.H., Guo, Z.B., Han, G.C., Li, K.B., Qiu, J.J., Xie, H., Luo, P. (2002-09). Multistate per-cell magnetoresistive random-access memory written at curie point. IEEE Transactions on Magnetics 38 (5 I) : 2850-2852. ScholarBank@NUS Repository.
Abstract: 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.
Source Title: IEEE Transactions on Magnetics
ISSN: 00189464
DOI: 10.1109/TMAG.2002.802858
Appears in Collections:Staff Publications

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