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Magneto-optical Kerr effect (MOKE) is used to investigate 1-D arrays of hexagonally arranged Co Y-junction nanostructures embedded in Anodic aluminium oxide (AAO) templates. MOKE in reflection mode clearly distinguishes the magnetic response on the front and back sides of two magnetic samples, i.e., in the form of solid nanowires and as hollow nanotubes. MOKE, being a surface sensitive technique, clearly shows the effect of magnetic interactions and density on magnetization reversal measurements. The experimental measurements complement well with the simulation results using MAGPAR. Simulations suggest the formation of closed vortex state in hollow nanotubes prominently and are found to be consistent with the MOKE measurements. Our approach also clearly shows that it is possible to study and model the exact profile of the Y-shaped nanowires. Their magnetization state is important and will have a significant impact on the overall magnetization as well as the switching behaviour of the nanowires. [ABSTRACT FROM AUTHOR]

Magnetic hollow nanotubes of cobalt forming close-packed arrays are synthesized by controlling the growth during electrodeposition in AAO template. Superconducting quantum interference device (SQUID) magnetometry is used to experimentally measure the static magnetization of the array of nanotubes. Excellent qualitative agreements of SQUID and micromagnetic simulations for static measurements are observed. This motivates us to evaluate dynamic response measurements via micromagnetic simulations. The coercivity simulated along the longitudinal axis of the nanotube is found increase with the length of isolated as well as for array of nanotubes. The effect of interactions is also clearly observed both in static as well as in dynamic evaluations. The interactions cause reduction in coercivity along with the switching which depends upon the length of the nanotubes. The calculation for FMR modes also indicates that propagation of the spin waves are greatly influenced by the hollow centre of nanotube as compare to nanowire and support to maintain the stable vortex configuration. For array of nanotubes, multiple peaks are found over larger number of frequencies which is anticipated due the interactions between nanotubes. Simulation for bias field and angular dependence of spin wave modes also yields a significant influenced by the presence of neighbouring nanotubes. [ABSTRACT FROM AUTHOR]

The magneto-optical Kerr effect (MOKE) is a powerful technique to investigate the magnetization behaviour in magnetic nanostructures. We describe the design of a polar MOKE instrument for investigating the magnetization variation in MOKE signal observed in the exciting regime where the size of the magnetic nanostructures is around 20-350 nm. In particular, when the magnetization of the sample is perpendicular to its plane (i.e., along the axis of a cylindrical nanowire) we use polar MOKE configuration. The sign and magnitude of the small rotation measured in the signal is found proportional to the magnetization and its direction. The MOKE measurements indicate that the hysteresis depends on the shape as well as the density of nanostructures formed. The instrument is sensitive enough to clearly indicate the effect of magneto-static interaction on shape of M-H loop. We have observed the coercive field of ~269G for cylindrical nanowire grown in anodic aluminium oxide template and ~135G for "pin" shaped nanowire grown in polycarbonate track etched template. The magnetization reversal measurements are intricate in the case of "pin" or "X" shaped nanostructures as seen from the loop. These typical MOKE measurements on the 1-dimensional (1-D) nanostructures explore the effect of magneto-static interaction between the nanostructures. [ABSTRACT FROM AUTHOR]