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Reorientation Response of Magnetic Microspheres Attached to Gold Electrodes Under an Applied Magnetic Field

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In this work, we report the mechanical reorientation of thiolated ferromagnetic microspheres bridging a pair of gold electrodes under an external magnetic field. When an external magnetic field (7 kG) is applied during the measurement of the current–voltage characteristics of a carboxyl ferromagnetic microsphere (4 μm diameter) attached to two gold electrodes by self-assembled monolayers (SAMs) of octane dithiol (C8H18S2), the current signal is distorted. Rather than due to magnetoresistance, this effect is caused by a mechanical reorientation of the ferromagnetic sphere, which alters the number of SAMs between the sphere and the electrodes and therefore affects conduction. To study the physical reorientation of the ferromagnetic particles, we measure their hysteresis loops while suspended in a liquid solution.

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This work was supported by the European Union Program ALBAN (grant no. E06D101257PE) and the Cambridge Overseas Trust. The work in Brazil was supported by CAPES. The work in Japan was supported by the Japan Society for the Promotion of Science (Furusato FU036), Grants-in-Aid for Scientific Research on Innovative Areas (no. 20108011, π-Space) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), a Collaborative Research Project of the Materials and Structures Laboratory, Tokyo Institute of Technology and the World Class University Program, Sunchon National University, Korea. The authors are indebted to Dr. Norio Okabayashi from the Tokyo Institute of Technology and Miss Lizbet Leon from the University of Brasilia for their help during different stages of the experiment.

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Correspondence to L. De Los Santos Valladares.

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De Los Santos Valladares, L., Dominguez, A.B., Aguiar, J.A. et al. Reorientation Response of Magnetic Microspheres Attached to Gold Electrodes Under an Applied Magnetic Field. Braz J Phys 43, 209–213 (2013).

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