Collective Magnetoresistance Effect of Ferromagnetic Microparticle Suspension

Abstract

The study of magnetic micro-/nano-particle suspensions as a magnetorheology material has been attracting much attention due to its possible applications in smart engineering as a kind of intelligent materials [1], [2]. Recently, enhancement and/or controllability of the magnetoresistance (MR) effect have become important issues for applications of magnetic micro-particle suspensions [3]. The magnetic particle suspension is a dispersing liquid of micron-sized ferromagnetic metallic particles. As a flowable ferromagnetic metallic material without any field (it is not easy to flow under the magnetic field), it necessarily exists the MR effect under applied magnetic field. Therefore, understanding and control of the magnetic suspension MR effect is one of important topics for electrical applications of magnetic suspensions. In this work, we experimentally investigated the collective MR effect of magnetic micro-particle suspensions. The magnetic suspension is based on ferromagnetic carbonyl iron microparticles, which is dispersed in the silicone oil with various surfactants. The magnetic suspension MR effect was intensively examined with changing the strength and the direction of the external magnetic field. As shown in Fig. 1, we have observed that the electrical resistance of magnetic suspensions was affected by the strength and the direction of the external magnetic field. The magnetorheological effect is attributed to the collective dynamic behavior of microparticles in the magnetic suspension under the magnetic fields.