Magnetization reversal in bent nanofibers of different cross-sections

Abstract

Artificial ferromagnetic nanofiber networks with new electronic, magnetic, mechanical and other physical properties can be prepared by electrospinning and may be regarded as the base of bio-inspired cognitive computing units. For this purpose, it is necessary to examine all relevant physical parameters of such nanofiber networks. Due to the more or less random arrangement of the nanofibers and the possibility of gaining bent nanofibers in this production process, elementary single nanofibers with varying bending radii, from straight fibers to those bent along half-circles, were investigated by micromagnetic simulations, using different angles with respect to the external magnetic field. As expected from the high aspect ratios and the resulting strong shape anisotropy, all magnetization reversal processes took place via domain wall processes. Changing the cross-section from circular to a circle-segment or a rectangle significantly altered the coercive fields and its dependence on the bending radius, especially for the magnetic field oriented perpendicular (90 deg) to the fiber axes. In all three cross-sections, an angle of 45° between the fiber orientation and the external magnetic field resulted in the smallest influence of the bending radius. The shapes of the longitudinal and transverse hysteresis curves showed strong differences, depending on cross-section, bending radius and orientation to the magnetic field, often depicting distinct transverse magnetization peaks perpendicular to the fibers for fibers which were not completely oriented parallel to the magnetic field. Varying these parameters thus provides a broad spectrum of magnetization reversal processes in magnetic nanofibers and correspondingly scenarios for a variety of fiber-based information processing.