Electronic transport and magnetoresistance in polycrystalline and epitaxialnanowires
- 15 February 2008
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 77 (5), 054417
- https://doi.org/10.1103/physrevb.77.054417
Abstract
We have studied and compared the electrical and magnetic behavior of sub-micron-sized polycrystalline and epitaxial chromium dioxide wires, grown using a selective-area growth technique. Low-temperature transport measurements have shown that the dc resistivity of polycrystalline wires is strongly dependent on the linewidth. Below a critical temperature, a transition from a positive to a negative temperature coefficient of resistivity is observed, which we attribute to a competition between the scattering of the conduction electrons inside the grains and scattering across the grain boundaries. Using a simple model based on grain boundary scattering, we can separate and quantify each type of scattering, and based on this, we estimate a mean transmission probability through the grain boundaries to be on the order of . Unlike polycrystalline wires, epitaxial wires behave in a highly metallic fashion, and a clear width-dependence is observed in the resistivity data for wires aligned along the axis, but not for those aligned along the axis. Furthermore, low-field magnetoresistance (MR) values have been measured as a function of magnetic fields applied both longitudinally and transversely. The results indicate that the MR behavior of polycrystalline wires is dominated by the shape anisotropy; however, for epitaxial wires, both the shape and magnetocrystalline anisotropy play important roles, and the resulting MR properties are found to be closely related to the orientation of the wire axis. By studying the MR curves, we inferred the internal magnetic domain structures in various single crystal wires and found that the spin-dependent transport is much stronger across a grain boundary than a magnetic domain wall.
Keywords
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