Magnetic interactions and reversal mechanisms in Co nanowire and nanotube arrays

Ordered hexagonal arrays of Co nanowires (NWs) and nanotubes (NTs), with diameters between 40 and 65 nm, were prepared by potentiostatic electrodeposition into suitably modified nanoporous alumina templates. The geometrical parameters of the NW/NT arrays were tuned by the pore etching process and deposition conditions. The magnetic interactions between NWs/NTs with different diameters were studied using first-order reversal curves (FORCs). From a quantitative analysis of the FORC measurements, we are able to obtain the profiles of the magnetic interactions and the coercive field distributions. In both NW and NT arrays, the magnetic interactions were found to increase with the diameter of the NWs/NTs, exhibiting higher values for NW arrays. A comparative study of the magnetization reversal processes was also performed by analyzing the angular dependence of the coercivity and correlating the experimental data with theoretical calculations based on a simple analytical model. The magnetization in the NW arrays is found to reverse by the nucleation and propagation of a transverse-like domain wall; on the other hand, for the NT arrays a non-monotonic behavior occurs above a diameter of ∼ 50 nm, revealing a transition between the vortex and transverse reversal modes. © 2013 American Institute of Physics.M.P.P. and C.T.S. are thankful to FCT for doctoral and post-doctoral Grants SFRH/BD/43440/2008 and SFRH/BPD/82010/2011, respectively. J.E. acknowledges financial support from FONDECYT 1110784, Grant ICM P10-061-F by the Fondo de Innovación para la Competitividad-MINECON, AFOSR FA9550-11-1-0347 and the Financiamiento Basal para Centros Científicos y Tecnológicos de Excelencia FB0807. J.V. acknowledges financial support through FSE/POPH. M.V. thanks the Spanish Ministry of Economia y Competitividad, MEC, under project MAT2010-20798-C05-01 and Spanish-Chilean CSIC-USACH Bilateral Project 2010CL0018. J.P.A. also thanks the Fundação Gulbenkian for its financial support within the “Programa Gulbenkian de Estímulo à Investigação Científica.Peer Reviewe