Tuning electronic transport in cobalt-filled carbon nanotubes using magnetic fields.

Metal-filled and decorated carbon nanotubes represent a class of quasi one-dimensional hybrid systems with enormous potential for applications in nanoelectronics and spintronics. Here we show that is possible to control the electrical conduction in ferromagnetic metal-filled carbon nanotubes by means of external magnetic fields, suggesting specific dimensionality-dependent conduction regimes. By increasing the magnetic field, we drive the charge flow from a positive to a negative magneto-conductance, revealing channel-selective conduction. Furthermore, the zero-field current temperature dependence shows different regimes, suggesting that the inter-shell hopping, assisted by the cobalt clusters, plays a key role in the dimensional crossover. The possibility of engineering and controlling the nature and size of the conducting shells and the filling with magnetic materials can allow the implementation of these systems in tunable hybrid nano-sensors and multifunctional magnetic devices.