Controlling structural and magnetic properties in CoNi and CoNiFe nanowire arrays by fine-tuning of Fe content

Herein, Co70Ni30 and CoxNiyFez (45 <= x <= 70; 22 <= y <= 33; 5 <= z <= 30) nanowire (NW) arrays with a length of approximately 15 mu m and diameter of 30 nm have been fabricated using a pulse electrochemical deposition technique in anodic aluminum oxide templates. Increasing the Fe additive concentration (ranging between 0.0035 and 0.05 M) in electrolyte solution has a considerable effect on the composition and crystalline characteristics of the resulting NW arrays, changing the hcp-Co and fcc-Ni phases into the bcc-Fe phase in Co45Ni25Fe30 NWs. On the other hand, hysteresis curves obtained from Co70Ni30 NWs show that, while the average coercivity (H-c(Hyst)) of parallel and perpendicular applied fields is nearly the same (H-c(Hyst) similar to 400 Oe), the corresponding squareness ratio is greater in the latter case, indicating a perpendicular anisotropy of NWs. Changing the Fe content in the range of 8-11% causes shape anisotropy to dominate the CoNiFe NW system with the bcc-Fe crystalline phase, allowing for controllable magnetic properties. The advanced analysis of angular first-order reversal curves (AFORCs; 0 degrees <= theta <= 90 degrees) revealed that the FORC coercivity (H-c(FORC)) in Co62Ni29Fe9 NWs increases from 700 Oe at theta = 0 degrees to 950 Oe at theta = 90 degrees, thereby evidencing a vortex domain wall mode (VDW). However, for Co55Ni22Fe23 NWs with a dominant bcc-Fe phase, HcFORC reaches 2700 Oe at theta = 77 degrees, starting from 1400 Oe at theta = 0 degrees. In addition to occurring the VDW mode, a single vortex appeared in the Co55Ni22Fe23 NWs when 68 degrees <= theta <= 77 degrees, followed by its annihilation for theta > 77 degrees. (C) 2018 Elsevier B.V. All rights reserved.