CoPt nanoscale structures with different geometry prepared by electrodeposition for modulation of their magnetic properties

Different nanoscale structures of CoPt have been prepared by electrodeposition. Nonmagnetic materials were used in all cases, so that the substrates did not interfere in the magnetic properties of the deposits. Thin films of 200–300 nm-thick were obtained on glass/ITO substrates; nanoparticles of 150 nm of diameter were obtained over silicon; nanowires of 100–200 nm of diameter and 14 μm length were obtained by using polycarbonate membranes sputtered with Au. All deposited geometries had a fixed composition (68–71 wt.% Pt) and crystalline structure typical of Co-hcp, distorted due to platinum incorporation. A study of the magnetic properties of the different geometries was performed. Dramatic changes in magnetism have been detected, related to the shape of the nanostructures: nanowires presented the lowest coercivity (330–700 Oe), thin films had a coercivity value of 850 Oe, while nanoparticles had the highest coercivity (2040 Oe). These coercivity variations were caused by different anisotropy contributions, depending on the geometry. The corrosion resistance test has been performed to determine the viability of the prepared nanostructures, nanostructures with higher exposed surface area had increase tendency to oxidation.

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► Different nanoscale structures as thin films, nanoparticles and nanowires of CoPt have been prepared by electrodeposition, all of them with a fixed composition of (68–71 wt.% Pt) and hcp crystalline structure.
► Magnetic properties of the different geometries have been performed showing drastic changes in magnetism related to the shape of the nanostructures.
► Hard magnetic properties can be enhanced by changing the deposit shape. The highest coercivity was in the sense: nanoparticles > thin films > nanowires with high aspect ratio, although different anisotropy contributions should be taken into account depending on the geometry.
► The corrosion resistance test reveal the viability of the prepared nanostructures, however nanostructures with higher exposed surface area had increase tendency to oxidation.