Effect of shape and magnetocrystalline anisotropies in ordered Co nanorod arrays with smaller diameter

Template assisted growth of Co nanorod arrays through electrochemical route was investigated. During this investigation, the template with nano-pore diameter was kept at a fixed value of 45 nm, whereas the length of the as grown nanorod array was varied from 25 to 400 nm keeping in mind that the aspect ratio (L/D) covers both below and above the unity. X-ray diffraction patterns indicate that the nanorod arrays initiate its textured growth with fcc (111) phase, however, the change in growth texture to hcp (100) was observed as it grows above 200 nm in length. The anisotropy fields extracted from the measured magnetization data reveal that a cross-over from in-plane to out-of-plane anisotropy takes place for L/D∼2.0. Based on the analytical approach, it seems that the shape anisotropy originated from the demagnetization factor with the change in geometry and magnetostatic interaction among the nanorods cause this crossover. However the micromagnetic simulation yields that both magnetocrystalline anisotropy and the magnetostatic interaction along with shape anisotropy are very much important to explain the experimental observations.