  Segmented magnetic nanowires are a promising route for the development of
three dimensional data storage techniques. Such devices require a control of
the coercive field and the coupling mechanisms between individual magnetic
elements. In our study, we investigate electrodeposited nanomagnets within host
templates using vibrating sample magnetometry and observe a strong dependence
between nanowire length and coercive field (25 nm to 5 $\mu$m) and diameter (25
nm to 45 nm). A transition from a magnetization reversal through coherent
rotation to domain wall propagation is observed at an aspect ratio of
approximately 2. Our results are further reinforced via micromagnetic
simulations and angle dependent hysteresis loops. The found behavior is
exploited to create nanowires consisting of a fixed and a free segment in a
spin-valve like structure. The wires are released from the membrane and
electrically contacted, displaying a giant magnetoresistance effect that is
attributed to individual switching of the coupled nanomagnets. We develop a
simple analytical model to describe the observed switching phenomena and to
predict stable and unstable regimes in coupled nanomagnets of certain
geometries.
