  We report an improved fabrication scheme for carbon based nanospintronic
devices and demonstrate the necessity for a careful data analysis to
investigate the fundamental physical mechanisms leading to magnetoresistance.
The processing with a low-density polymer and an optimised recipe allows us to
improve the electrical, magnetic and structural quality of ferromagnetic
Permalloy contacts on lateral carbon nanotube (CNT) quantum dot spin valve
devices, with comparable results for thermal and sputter deposition of the
material. We show that spintronic nanostructures require an extended data
analysis, since the magnetisation can affect all characteristic parameters of
the conductance features and lead to seemingly anomalous spin transport. In
addition, we report measurements on CNT quantum dot spin valves that seem not
to be compatible with the orthodox theories for spin transport in such
structures.
