RESEARCH ARTICLE Copyright © 2012 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Nanoscience and Nanotechnology Vol. 12, 1–8, 2012 Template-Assisted CoPd Nanowire Arrays: Magnetic Properties and FORC Analysis V. Vega 1 , W. O. Rosa 1 , J. García 1 , T. Sánchez 1 , J. D. Santos 1 , F. Béron 2 , K. R. Pirota 2 , V. M. Prida 1 ∗ , and B. Hernando 1 1 Depto. de Física, Universidad de Oviedo, Calvo Sotelo s/n, 33007-Oviedo, Asturias, Spain 2 Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, Rua Sergio Buarque de Holanda, 777, Cidade Universitária “Zeferino Vaz,” Campinas 13083-859, SP, Brazil Highly hexagonally ordered CoPd alloy nanowire arrays were synthesized through electrochemical deposition techniques into the nanopores of anodic alumina membranes used as templates. Two different electrolytes were used for this purpose, one with pH = 41 and the other with pH = 7. Under applying different electrodeposition parameters and by adjusting both, the current density and the electrolyte composition, it could be possible make to vary the composition of CoPd alloy nanowires in a wide range. Their composition and morphology were investigated by SEM and EDX. The magnetic properties of the nanowires array have been measured with a VSM as a function of the temperature, ranging from RT down to 50 K, for different CoPd alloy nanowires composition. Also, the temperature influence on the reversible-irreversible magnetization processes related with the magnetization reversal of the CoPd nanowires array has been analyzed by first order reversal curve (FORC) method. Keywords: Nanoporous Anodic Alumina, Electrodeposition, Nanowires, Magnetization Reversal Process. 1. INTRODUCTION Template-assisted electrodeposition is a useful and low- cost technique for synthesizing metallic nanomaterials with controlled shape and size. Self-organized arrays of nanostructured materials having specific arrangements can be prepared by template-assisted electrodeposition process, employing either an active or restrictive template as a cathode in an electrochemical cell, to synthesize metal- lic and magnetic nanostructures. 1 Metallic nanowires at nanometer scale exhibit unusual behavior of their elec- trical, electronic, thermoelectrical, optical, magnetic and chemical properties, which are different compared to their bulk counterparts. Such unusual properties have gener- ated a huge interest in nanostructured materials for poten- tial applications in biomedical sciences, electronics, optics, magnetism and energy storage. 2 The physical properties of nanowires are influenced by their composition and morphology, geometry and aspect ratio, carrier density of states, etc. Single nanowires hold lot of promises in many basic and applied research fields as electronic devices, junction diodes, transistors, FETs and logic gates, ∗ Author to whom correspondence should be addressed. thermomagnetic and thermoelectric cooling systems as well as in opto-electronic and biomedical applications. Moreover, periodic arrays of magnetic nanowires hold also high potential interest for technological applications such as ultra-high density data recording media and safe energy conversion and storage materials. 3–6 Although Pd is a paramagnetic metal, its alloys with Co or other ferromagnetic materials become ferromag- netic, even for Co additions as small as 0.1% at. 7–9 Co- Pd alloys also show interesting magnetic properties such as perpendicular magnetic anisotropy and high Kerr rota- tion effect. 10 11 Additionally, Co-Pd alloys exhibit other outstanding properties, i.e., good mechanical hardness and excellent corrosion resistance. 12 All of the above character- istics of CoPd alloys make them excellent candidates for technological applications in magnetic or magneto-optical information storage devices. 8 9 13 Therefore, the study of CoPd alloys is highly interesting from both applied and theoretical points of view, and a deep understanding of its magnetic features is needed to design technological applications. Although the synthesis of CoPd alloys by other methods such as arc-furnace, 14 e-beam evaporation, 15 laser ablation 10 or sputtering 16 have been widely reported, electrodeposition of CoPd alloy nanowires has not been J. Nanosci. Nanotechnol. 2012, Vol. 12, No. xx 1533-4880/2012/12/001/008 doi:10.1166/jnn.2012.4908 1