Structural and Magnetic Characterization of FeCoCu/Cu Multilayer Nanowire Arrays

A series of [FeCoCu/Cu(x)]10 (7 ≤ × ≤ 40 nm with FeCoCu layer thickness of 300 nm) and [FeCoCu(y)/Cu]10 (120 ≤ y ≤ 900 nm with Cu layer thickness of 15 nm) arrays of multilayer nanowires, 35 nm in diameter, were fabricated by electrodeposition into self-assembled pores of anodic alumina membranes. High-resolution transmission electron microscopy and X-ray diffraction analysis confirm the segregation of layered structures, with well-defined Cu layers (fcc cubic structure) separating FeCoCu-alloy segments (bcc cubic structure). Hysteresis loop measurements indicate an overall magnetization easy axis parallel to the nanowires in all the samples. For constant FeCoCu segment length, the coercivity, the remanence, and especially, the susceptibility increase with the Cu layer thickness, whereas for the series with constant Cu layer thickness, the susceptibility significantly decreases with FeCoCu segment length. Complementary Henkel curves indicate that the net inter/intrananowires magnetostatic interactions always contribute to the demagnetization of the nanowires. The variation of the susceptibility with FeCoCu and Cu layers thickness together with the Henkel plots data indicate that a reduced demagnetizing effect is achieved for multilayer nanowires with the thicker Cu layer and the shorter FeCoCu segment, for which a moderated reduction in saturation magnetization of around 11% is estimated compared to a continuous FeCoCu alloy nanowire array.