Hitoshi Iwasaki

Magnetism of Co/sub 1-x/Fe/sub x/-NOL in specular spin-valves

We investigated the magnetic properties of the Co/sub 1-x/Fe/sub x/-natural oxidized nano-oxide layer (NOL) in the specular spin-valve system by precise measurement of magnetization at 77 K and M-T curves after field cooling at /spl plusmn/5 kOe. The result suggests the antiferromagnetic component behavior of the NOL and its Ne/spl acute/el temperature (T/sub N/) shifts to the higher temperature with increasing Fe composition. Below the T/sub N/, the antiparallel spin configuration at the pinned layers is stabilized by the exchange bias field induced from antiferromagnetic component of NOL by the field cooling in negative field direction.

Confirmation of the “Atom Pumping-Up Mechanism” in Fe/Ta Film for the Fabrication of Ferromagnetic Nanobridges

When the surface energy of bottom layer is lower than top layer, the atoms of bottom layer should be pumped up at the triple point of the grain boundary. This phenomenon should be useful for the fabrication of well-defined nanobridge. To confirm the Atom Pumping-Up mechanism for metal/metal thin films, Ta(2 nm) on epitaxial MgO(001)/Fe(001) films were prepared by the electron beam deposition method. The Pumping-Up mechanism was successfully confirmed by the Auger Electron Spectroscopy, the in situ Scanning Tunneling Microscopy, and the Transmission Electron Microscope observation after heat treatment of 400 degCtimes30 min. The size of the Fe bridges was 2-5 nm. Furthermore, the magnetic exchange coupling effect on the magnetization process through the ferromagnetic bridges between two Fe layers in MgO/Fe/Ta/Fe after Atom Pumping-Up shows a good agreement to the micromagnetics simulation result from the assumption of ferromagnetic bridges with the size of 1-4 nm

Room temperature NOL exchange biasing superimposed on AFM exchange bias in specular spin-valves

To confirm the origin of the exchange field from nano-oxide layer (NOL), the detailed analyses of the magnetization curve and the temperature dependence on magnetization for the Co/sub 1-x/Fe/sub x/-NOL inserted samples were investigated. The room temperature NOL exchange biasing superimposed on AFM exchange bias in specular spin-valve (SPSV) is also considered to realize CIPGMR (current in plane giant magnetoresistance) with higher sensitivity and a more stable pinned layer for high density magnetic recording head.