Preparation of polymer-based composites with magnetic anisotropy by oriented carbon nanotube dispersion

A polymer-based nanocomposite film with partially oriented multi wall carbon nanotubes (MWCNTs) was synthesized by a facile technique. A small amount of MWCNTs (average diameter 50 nm, length 500 μm) containing ferromagnetic iron particles, mainly localized in the tips, were dispersed ultrasonically for over 30 h in a diacrylate resin (bisphenol-A-diglycydylether diacrylate, BHEDA). The liquid resin was cast between two UV transparent substrates and subjected to a unidirectional magnetic field before the mixture had been cationic photopolymerized. Magnetization and magnetoresistance measurements were performed at room temperature on the solid films produced both with zero and with an external magnetic field perpendicular with respect to the plane of the film. A complex anisotropic response has been observed and a simple model was developed to explain the results consistent with some ordering effect occurred by the application of the external magnetic field.