Size effects on magnetic properties in Fe 0.68 Ni 0.32 alloy nanowire arrays

Using electrochemical deposition, 4mm long Fe0.68Ni0.32 alloy nanowire arrays with diameters in the range of 16– 100 nm are fabricated in porous anodic alumina films. The results indicate that all of the Fe0.68Ni0.32 alloy nanowire arrays with different diameters are stabilized in a BCC structure with a [1 1 0] texture oriented along the long axis of the nanowires. For the whole diameter range of the nanowires, the easy magnetization axis is parallel to the nanowire long axis. With increasing diameter, the coercivities obtained both in parallel and perpendicular directions decrease. For nanowire arrays with larger diameters, the coercivity has a maximum when the applied field is perpendicular to the long axis of the nanowires, which is different from the results for nanowire arrays with smaller diameters. This different coercivity behaviour is discussed by considering the shape anisotropy, magnetocrystalline anisotropy and the dipolar interaction between the nanowires. r 2002 Elsevier Science B.V. All rights reserved. PACS: 75.50.S; 76.60.E