A Study on the Switching Characteristics of NiFe/Co/Cu/Co Pseudo Spin Valve MRAM Cells

概要

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NiFe(60A)/Co(5A)/Cu(60A)/Co(30A) pseudo spin valve (PSV) thin films were prepared on Cu(50A)/Si(111, 4 degree tilt-cut) templates by a RF magnetron sputtering system and patterned into micron sized magnetoresistive random access memory (MRAM) cells using conventional optical lithographic processed. When the switching properties of PSV MRAM cells were investigated with respect to the cell geometry, the cells showed a few mV of output voltrage in constant 1 mA of sense current and much sensitive variation of switching thresholds of both soft and hard layers consisting of the cells. In order to reduce the switching thresholds of magnetic layers in micro cells, which is an obstacle of realization of a competitive MRAM device, a new approach has been introduced using the control of shape anisotropy of the cells. By an appropriate combination of two anisotropy terms, shape anisotropy of the cells and magnetocrystalline uniaxial anisotropy of sheet films, the switching threshold of NiFe(60A)/Co(5A) soft layer could be decreased from about 15 Oe to 5 Oe and the concept has been thought to be useful for a practical PSV MRAM device.
社団法人電子情報通信学会の論文
1999-11-10