Magnetic nanowire arrays and their temperature stability Dissertation

Magnetic nanowire arrays and their temperature stability - Dissertation Example These nanowires are hexagonally arranged and highly ordered with wire to wire distances between 30 to 100 nm, wire diameters of 5 to 250 nm and lengths up to several ÃŽ ¼m depending on the preparation conditions. Ferromagnetic nanowires with diameters in the range of domain wall widths or even smaller are expected to behave as single domain particles. In the easiest case such nanowires can be interpreted as defect-free long ellipsoids with homogeneous magnetization and these represent model systems for the investigation of magnetic interactions because their magnetic properties are not obscured by difficult-to-control bulk domains. Within such nanowires the shape anisotropy, the magneto-crystalline anisotropy and – in the case of very fine nanowires (diameters about 5 nm) – the influence of the surface magnetism has to be considered. Depending on the distance between the nanowires the wires can be interpreted as magnetically isolated magnetic mono-domains or, in the case of arrays in alumina, as dipolar interacting mono-domains. For the understanding of the behavior of such arrays both theoretical and experimental investigations are essential. In the following we will just prese nt experimental results which demonstrate the basic magnetic properties.... Fig:- Hexagonally arranged Nanowire Arrays Ferromagnetic nanowires with diameters in the range of domain wall widths or even smaller are expected to behave as single domain particles. In the easiest case such nanowires can be interpreted as defect-free long ellipsoids with homogeneous magnetization and these represent model systems for the investigation of magnetic interactions because their magnetic properties are not obscured by difficult-to-control bulk domains. Within such nanowires the shape anisotropy, the magneto-crystalline anisotropy and – in the case of very fine nanowires (diameters about 5 nm) – the influence of the surface magnetism has to be considered. Depending on the distance between the nanowires the wires can be interpreted as magnetically isolated magnetic mono-domains or, in the case of arrays in alumina, as dipolar interacting mono-domains. For the understanding of the behavior of such arrays both theoretical and experimental investigations are ess ential. In the following we will just present experimental results which demonstrate the basic magnetic properties. Hysteresis loops of arrays of Co-nanowires in alumina with different diameters and roughly the same length with H parallel (II) and perpendicular (^) to the long wire axis. Aside from the scientific attitude such arrays of ferromagnetic nanostructures are of significant interest because of their possible application as ultrahigh-density magnetic recording media. The preparation of such systems is very cheap and fast compared to expensive and time consuming methods as microlithography and molecular beam epitaxy. In addition the diameter, interwire