Magnetization reversal dependence on effective magnetic anisotropy in electroplated Co–Cu nanowire arrays

Abstract

Arrays of Co (100-x) Cu (x) (0 ≤ x ≤ 27) nanowires with 45 nm of diameter and 18 µm in length, have been potentiostatically electrodeposited into the hexagonally self-assembled nanopores of anodic alumina membranes. The structural characterization of Co-Cu nanowires confirms the coexistence of both hcp and fcc crystalline phases, with textures that are strongly affected by the fractional content of Cu. Parallel magnetic studies of the room temperature magnetization process by First Order Reversal Curve (FORC) analysis and the angular dependence of coercivity, confirm the presence of two coexisting ferromagnetic phases at intermediate Cu content nanowires, ascribed to a softer magnetic phase for pure Co and a harder magnetic one for the Co-Cu composition alloy, respectively. The temperature dependence of coercivity and remanence reveal a reorientation of the effective magnetic anisotropy with adding Cu into the Co-Cu alloy nanowires, being enhanced by the coexistence of the two ferromagnetic phases.

Tailoring magnetic properties in arrays of pulse-electrodeposited Co nanowires: The role of Cu additive

“…Furthermore, no shifts in the XRD peaks are observed, so that CoCu solid solution alloys cannot be indicated [39,40]. However, based on the recent study on CoCu NW arrays obtained by dc electrodeposition, for a small Cu content (e.g., Co 92 Cu 8 ), (110)-hcp peak in pure Co NWs disappeared and a (200)-fcc Co reflection emerged due to the addition of Cu [38].…”

“…8(a). According to FORC investigations by Garcia et al [38], in the case of 45 nm diameter Co 92 Cu 8 NWs obtained using dc electrodeposition, the FORC analysis revealed a coexistence of interacting soft and hard phases. The former phase corresponded to a pure Colike NW array and the latter phase was ascribed to a Co-Cu phase, coinciding with a decrease in the hcp phase and the appearance of (200)-fcc phase.…”

“…Also, it is worth mentioning that, according to Liu et al, crystalline structure of Co-rich CoCu NWs is dominated by the hcp-Co with a (100) preferential peak [37]. Additionally, using a dc electrodeposition method together with a pH solution of 4, Garcia et al [38] found a coexistence of both hcp and face-centered cubic (fcc) crystalline phases in pure Co and CoCu NW arrays with a diameter of 45 nm. In this case, the crystalline textures of CoCu NWs were significantly affected by the content of Cu.…”

Influence of shape and dimension on magnetic anisotropies and magnetization reversal of Py, Fe, and Co nano-objects with four-fold symmetry

“…[10][11][12][13][14] In our previous works, fourfold iron nanostructures built of four crossing nanowires were already proven to show hysteresis loops with steps along the slope of the curve, which can be attributed to four unambiguously distinguishable states in vanishing external magnetic field. 15,16 Since these systems exhibit four global net magnetization states, which can be detected without the necessity to introduce further symmetry-breaking coatings, 17 they can be utilized for novel quaternary storage devices, storing two bits per single memory cell.…”

Ni-Co Alloy and Multisegmented Ni/Co Nanowire Arrays Modulated in Composition: Structural Characterization and Magnetic Properties

“…Among the solid template-based growth methods, the template-assisted electrochemical deposition of single metals and their alloys is one of the most efficient and versatile growing technique popularly employed for the synthesis of 1D nanomaterials embedded inside the pores of polymeric or anodic aluminum oxide (AAO) membranes [16][17][18][19]. The synthesis of nanomaterials through the template-assisted electrodeposition method by employing nanoporous alumina membranes (NAMs) as patterned templates, is a commonly used technique for the growing of metallic and magnetic nanostructures inside the pores of anodic alumina with a wire shape geometry and in the nanometer scale range (typically between 20 to 200 nm in diameter size) [20,21]. In comparison with track-etched polycarbonate membranes, which usually exhibit crossed nanopores, the anodic alumina templates provide hexagonal close-packed arrangement of parallel aligned nanopores in a honeycomb spatial structure having a well-defined cylindrical shape, in which can be embedded the electrochemically-grown magnetic NWs by replicating the same dimensions than the former pore sizes.…”