Shape-anisotropic nickel-PDMS composites with uniaxial magnetic anisotropy obtained by emulsification under magnetic field

Abstract

"Magnetic microcomposites were fabricated by emulsification of a mixture of polydimethylsiloxane (PDMS) and nickel microparticles. The composites were obtained in a temperature-controlled water-surfactant media with and without the influence of an external magnetic field. The presence of a moderate external magnetic field of 80 G (8 mT) during the polymerization stage leads to the arrangement of nickel microparticles into chains that form the magnetic core of the synthesized composites. The method allows controlling the shape of the composite particles by applying a magnetic field and varying the stirring speed. Three shapes of composite particles, namely spherical, teardrops, and ellipsoidal, were obtained and magnetically characterized. Room temperature hysteresis loops and dM/dH versus H curves in the second-to-third quadrants show that spherical particles are isotropic while non-spherical particles show an induced uniaxial magnetic anisotropy which depends on the shape of the resulting composite particles."