Conversion of magnetic anisotropy in electrodeposited Co-Ni alloy nanowires

In this paper, the influence of alternating current (ac) electrodeposition frequency and waveform is reported on chemical composition, microstructure and consequently magnetic properties of Co-Ni binary alloy nanowire arrays embedded in an alumina template. For sinusoidal and square electrodeposition waveforms the easy axis of magnetization rotates from being parallel to perpendicular orientation to nanowire long axis as the deposition frequency increases from 200 to 800 Hz. The reason for the drastic change of magnetic anisotropy in nanowires is attributed to the increase of cobalt content and the crystal structure phase transformation from fcc-hcp mixture at high Ni content to hcp at high Co content. We explain the conversion of magnetic behavior of nanowire arrays in terms of a competition between the shape and magnetocrystalline anisotropies.