Toward robust segmented nanowires : understanding the impact of crystallographic texture on the quality of segment interfaces in magnetic metallic nanowires

摘要

Segmented nanowires (NWs) have found a wealth of applications due to their multifuctionality, arising from complementarities and synergies among segments of different materials. However, to ensure a practical use of segmented NWs, high quality interfaces between dissimilar segments must be ensured. Herein, tri-segmented CoPt/Cu/Ni NWs and bi-segmented CoPt/Ni magnetic NWs are fabricated by means of template-assisted electrodeposition and the characteristics of their interfaces are investigated in detail. The presence of a Cu segment sandwiched between the CoPt and the Ni segments severely affects the integrity of the whole NW. Namely, Cu deposits in a (200) textured face-centered cubic (fcc) structure, which cannot accommodate well on the c-axis oriented hexagonal close-packed CoPt. Instead, when the Cu segment is absent, well-connected CoPt/Ni NWs with smooth interface are obtained. Unlike the Cu segment, Ni shows the (111) textured fcc structure, which holds good crystallographic matching with the underlying CoPt segment. Magnetic measurements reveal that CoPt/Ni NWs exhibit staircase-like hysteresis loops similar to the tri-segmented CoPt/Cu/Ni NWs. Such loop shape stems from the dissimilar coercivity between the hard (CoPt) and soft (Ni) segments. The bi-segmented NWs (with robust interfaces) are appealing for multi-bit recording media, magnetic nanoelectromechanical systems and magnetically-driven wireless drug delivery nanoplatforms.