Insight into the Intra and Inter-wire Magnetic Interactions of Co Nanowire Arrays by FORC Diagrams

Abstract

Understanding and controlling the magnetic behavior of nanowire (NW) arrays is a fundamental step for developing novel future-generation devices. The current research investigated the role of copper pre-plating thickness on the structural and magnetic interactions of cobalt NW arrays. The NWs were grown in the anodic aluminum oxide (AAO) templates with a nanopore diameter of 30 nm by using a pulse electrodeposition (PED). The thickness of Cu pre-plating varied by adjusting the amount of electrodeposition (ED) Coulomb charge to about 0.03–0.7 C. The intensity of the Co-hcp peaks in the X-ray diffraction (XRD) pattern changes with the increase of Cu pre-plating, which can be related to ion mobility and growth kinetics during the ED process. The hysteresis curves indicate that effective magnetic anisotropy fields (\({\text{H}}_{\text{A}}^{\text{eff}})\) increase from 7200 to 11,000 Oe with increasing Cu thickness. The coercivity of Co nanowire arrays without Cu pre-plating was 1170 Oe and rose to 1870 Oe for optimum Cu thickness with 0.3 C pre-plating. The switching field distribution (SFD) extracted from hysteresis curves agrees well with the squareness ratio. Also, the SFD indicates an exchange coupling between the interfaces of the magnetic phases in the optimum sample. The regions formed in the first-order reversal curve (FORC) diagram showed crystalline features and magnetic phase interactions between the intra and inter-wire. Further, the FORC analysis showed the same crystalline features as those obtained from the XRD structural analysis.