Ultra-High Density Magnetic Memory Cells

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We have investigated magnetic properties and magnetization processes of sub-micron magnetic memory cells in order to find a breakthrough that increases a density of MRAM (magnetic random access memory).(1) We have investigated method for recording magnetic memory. The magnetization direction of the asymmetric ring dots (material: 5-20 nm thick Ni-20at%Fe, diameter: 500-1000 nm) that have partly planed outer sides were controlled between clockwise and counterclockwise by in-plane magnetic fields, even though the ordinary ring dots needed the clockwise and counterclockwise magnetic fields caused by the perpendicular current.(2) We also have found that the cup-shaped magnetic memory cell required lower magnetic field to be recorded than the ring memory.(3) The Ni-Fe(10 nm)/Mn-Ir(10 nm) ring dot has fixed magnetization direction.(4) The information recorded in the magnetic memory can be detected using atomic force microscopy with conductive probe.