Shigekazu Sumita

Electrodeposition of Ferromagnetic Metal Nanowires

Ni-Fe alloy films and nanowires were fabricated using electrodeposition technique. The cylindrical shape of nanowires was precisely transferred from the nanochannels of membrane filters and the aspect ratio reached to around 60. Coercive force in in-plan direction of Ni-Fe alloy films decreased to ca. 1 Oe with increasing Fe content in deposits while, in perpendicular direction, the films were hardly magnetized. Magnetic hysteresis loops revealed that the nanowires were spontaneously magnetized to the long axis direction and the coercive force reached to ca. 200 Oe.

Fabrication of MRAM-type Structure and Their Magnetic Properties.

The characteristic points of MRAM are compared with those of DRAM, Flash memory, SRAM, and FeRAM. The differences in PSV-MRAM and MTJ-MRAM are discussed in terms of the directions of sense current, CIP or CPP, and connections of CMOS with MR elements.An MRAM-type structure was accomplished with three layers of PSV element, NiFe soft layer (6nm) /Cu non-magnetic layer (3-6nm) /Co hard magnetic layer (4nm) on Si-wafer. Each PSV element of 80nm X 150nm was sandwiched by a sense line and a word line at the intersection of these lines. Furthermore, switching phenomena, which were observed in magnetic hysteresis loop by using PSV thin films, are also discussed along with the size limitation of PSV dots.