Tunable Distribution of Magnetic Nanodiscs in an Array of Electrodeposited Multilayered Nanowires

Abstract

Co-Ni-Cu/Cu multilayered nanowire arrays were electrodeposited in polyester track etched (PETE) nanoporous template with appropriate hydrophilic properties in a single bath. The array of multilayered nanowires can provide a three-dimensional accumulation of magnetic nanodiscs in a non-magnetic media. Magnetic properties and microstructure of multilayered nanowires with different copper layer thickness were studied. Using different characterization techniques including X-ray diffraction (XRD), transmission electron microscope (TEM), magnetic force microscopy and magnetization curves, we observe the formation of unique sharply interfaced multisegmented magnetic/nonmagnetic nanowires in a range of spacing thickness from 0.7 nm to 26 nm. MFM shows that the filling of nanopores happens uniformly during electrodeposition in the form of nanowires, while TEM examinations confirm the formation of precise multilayered structure. TEM also reveals the formation of sharp interfaces between the segments with a polycrystalline superlattice structure. XRD interestingly shows that satellite peaks appear around (111) main Bragg reflection. The magnetization curves at 20 K of the array show a relative rotation of easy axis direction from out of the plane to in the plane, as the spacing Cu layer thickness ( t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Cu</sub> ) increases in a range of 0.7-26 nm. The variation of measured coercivity in different bi-layer thicknesses likely shows the intention of the structure to form discrete magnetic segments as the non-magnetic spacer layer becomes thicker. However, the variation of coercivity and squareness implies the existence of strong interaction between the segments. A study on the remanent magnetization at 20 K for t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Co-Ni-Cu</sub> =3.3 nm with a range of tCu reveals the existence of demagnetising interactions within each array suggesting the anti-ferromagnetic coupling between Co-Ni-Cu layers.