Magnetic anisotropy and one-dimensionality finite-size scaling law in polycrystalline Ni nanowire arrays

Abstract

Ordered Ni nanowire arrays were successfully fabricated by electrochemical deposition method based on the anodized aluminum oxide (AAO) templates. It was found that the diameter of nanowire can be well controlled by the pore size of AAO template. The nanowire arrays with 50nm in diameter were characterized by X-ray diffraction, electron microscopy, and physical properties measurement system. The results indicate that the polycrystalline Ni nanowire arrays exhibit obvious magnetic anisotropy, and the easy magnetization direction is oriented along the nanowire axial direction. By measuring the temperature dependence of magnetization, the Curie temperatures of nanowires with different sizes were obtained. The Curie temperature of one-dimensionality (1D) nanowire arrays is found to decrease with decreasing diameter and follow a finite-size scaling theory with λ=0.926 and ξ0=17.35Å. The fitting exponent of 1D nanowire arrays is close to the nanoparticles (zero-dimensionality, 0D) result and two-dimensionality (2D) nano-films result.