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Posted: March 9, 2007
Chinese develop new type of MRAM
(Nanowerk News) Thanks to its advantages such as data safety, anti-radiation, high speed, low density, energy-efficiency and long work life, the magnetic random access memory (MRAM) is considered a key device for the future computer, information and telecommunication technologies.
The new device consists of arrays of magnetic memory cells in which the information is stored as the magnetization direction of tiny ferromagnetic elements. In a conventional design scheme, writing these elements uses two crossed pulse currents to produce a synthesized magnetic field to reverse selected magnetic elements, and the read process relies on tunneling magneto-resistance (TMR) ratio.
Novel and conventional MRAM demo devices fabricated for a contrast experiment, showing the NR-MTJ memory cells and current switching technique can remarkably decrease the energy consumption and increase storage density. (Image: CAS)
With the joint support of National Basic Research Program (973 Program), the National Natural Science Foundation of China, and CAS Knowledge Innovation Program between 04/2002 and 09/2006, a research team led by Prof. HAN Xiufeng from the CAS Institute of Physics has recently developed a demo device for a new type of MRAM.
Instead of using the traditional way of fabrication, the researchers adopt a principle they have worked out that takes nano-ring-type magnetic tunnel junctions (NR-MTJs) with the outer- and inner-diameter of around 100 and 50 nm as memory cells and employs positive and negative pulse current to directly drive the rotation of magnetic moment on a bit plane.
Scientists say that their invention could overcome the difficulties of high energy consumption and low storage density, two bottleneck problems of MRAM development. Only 500 ∼ 650 µA (microampere) or less such a current is needed for a device cell to perform the writing operation, and 10 ∼ 20 µA (microampere) current can be used to perform the reading operation. After further improvement, it is expected to further decrease the writing current to 100 ∼ 200 µA (microampere).
Such a design concept and framework, according to researchers, could greatly upgrade the possibility of fabricating high-performance but low-cost MRAM.