Effect of the template-assisted electrodeposition parameters on the structure and magnetic properties of Co nanowire arrays Malgorzata Kac a,⇑ , Arkadiusz Zarzycki a , Slawomir Kac b , Marek Kopec a , Marcin Perzanowski a , Erazm M. Dutkiewicz a , Katarzyna Suchanek a , Alexey Maximenko a , Marta Marszalek a a Institute of Nuclear Physics Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Krakow, Poland b AGH University of Science and Technology, al. A. Mickiewicza 30, 30-059 Krakow, Poland article info Article history: Received 18 March 2016 Received in revised form 25 May 2016 Accepted 2 June 2016 Keywords: Co nanowires Electrodeposition Magnetic properties Polycarbonate membranes abstract We studied the magnetic properties of Co nanowires electrodeposited in polycarbonate membranes as a function of the electrodeposition and template parameters. We showed the response of the current as a function of time, for nanowires prepared in various conditions. X-ray diffraction measurements indicate that nanowires have polycrystalline hcp structure with small addition of fcc phase. Magnetic properties analyzed by SQUID measurements suggest that easy axis of magnetization follows the nanowire axis with coercivity increasing with a decrease of nanowire diameter and length. The largest coercivity, equal to 850 Oe, was obtained for nanowires with the diameter of 30 nm and the length of 1.5 lm. We find the coercivity to be insensitive to pH value. Low electrodeposition temperature, low cathodic potential, and medium pH are the synthesis parameters most beneficial for large coercivity and/or magnetic aniso- tropy with easy axis along nanowires. Ó 2016 Elsevier B.V. All rights reserved. 1. Introduction Nanowires are important building elements of micro- and nanoscale devices because, due to their size and high aspect ratio, they exhibit interesting physical and chemical properties. They can be used, for instance, as sensors, light-emitting diodes, lasers, com- ponents in electronic circuitry, high-density magnetic storage devices, and as flexible permanent magnets [1–5]. However, many applications require long-range ordering in two-dimensional arrays, which is still not well studied. Many techniques such as electron beam lithography, X-ray lithography, scanning probe lithography, nano-imprint, and porous template lithography have been used to fabricate single or segmented nanowires consisting of different elements. Among these methods, the template- assisted electrodeposition is particularly attractive due to its sim- plicity, low-cost, and a high yield. It presents an efficient way to manufacture isolated nanowire arrays with small diameters deter- mined by the pore diameter of the template. This simple method allows the production of nanowires in high volume and on large areas for fundamental studies and for the production of nanodevices. Many studies have been performed to determine the magnetic properties of metal nanowires [6–10]. Nanowires can be produced using either potentiostatic or galvanostatic mode, in polycarbonate or alumina membranes. Both types of templates have nanochan- nels with a defined diameter, but their properties and morphology influence deposition process differently. Membrane parameters (such as thickness, size, porosity and arrangement of pores), elec- trodeposition parameters (electrolyte composition, temperature, pH), as well as suitable electrodes and membranes preparation strongly affect the nanowires properties. Co nanowires are some of the most frequently studied because they exhibit high magnetic coercivity resulting from the shape ani- sotropy and orientation of nanowire assemblies. The studies usu- ally show an increase of coercivity value with a decrease of nanowire diameter and length, accompanied by easy axis of mag- netization along nanowires [11–15]. However, some previous studies have demonstrated an opposite relation showing a coerciv- ity reduction with an increase of the nanowire length [8],a decrease of the diameter [16,17] or non-monotonic behavior [17]. The coercivity value and magnetic anisotropy are also sensi- tive to the shape of pores [18] and template porosity [19]. Low porosity value [20] and high misalignment of nanowires [21] reduce dipolar interaction. Membrane parameters can also affect crystalline structure of nanowires, with small diameters promoting their single crystalline structure [11,22]. http://dx.doi.org/10.1016/j.mseb.2016.06.004 0921-5107/Ó 2016 Elsevier B.V. All rights reserved. ⇑ Corresponding author. E-mail address: malgorzata.kac@ifj.edu.pl (M. Kac). Materials Science and Engineering B 211 (2016) 75–84 Contents lists available at ScienceDirect Materials Science and Engineering B journal homepage: www.elsevier.com/locate/mseb