Preparation of Ferromagnetic Nano-dot system and Its Magneto-Resistance

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For the study of (spin dependent) electric properties of nano materials, the production of nano-electrodes, the design of special attatchment for transmission electron microscopy (TEM) and the quantum conductance (QC) of ferromagnetic nano-particle systems and nano-wires were investigated. The production of nano-structures and selection of the conduction paths were successfully carried out inside TEM. The set of results will contribute to the future research on the spin dependent conduction of nano-structured materials.1.Production of Nano-Electrodes : By the sputtering method using diamond particles as the mask, electrodes having nano-scaled tip and the length of several tens of μm could reproducibly prepared. Using these electrodes, conduction experiments inside TEM became possible.2.Design and Production of TEM Holders for Nano-Conduction Experiments : TEM holders to measure the nano-current between nano-dots were produced. Two electrodes can be loaded in the holder. Nano-manufactun … More ng and adequate selection of measuring positions were realized in nano-scale.3.Electric Measurements of Limited Number of Fe Nano-Particles : Using the 10nm thick Fe-SrF_2 films as the sample where Fe particles are embedded in SrF_2, the Coulomb blockade effect was detected. The sample was attached by the Au counter electrode, I-V measurements were performed at room temperature. When the contact area was less than 700nm^2, the Coulomb blocade of 0.4V was detected. The number of particles in this area is about 10.4.Quantum Conductance of Au and Fe Nano-Wires : Nano-wies of non-magnetic Au and ferro-magnetic Fe were studied inside TEM. In both cases, QC with half integer steps was recognized. The appearance of this phenomenon was influenced by the broken speed of wires, the magnetic field and the bias voltage. By adequate selection of experimental conditions, the wire showing the half integer step was kept more than 1 second. This is long enough to study the relationship between the wire shape and QC. Less