Since the discovery of carbon nanotubes in 1991 by Iijima¹, there has been great interest in creating long, continuous nanotubes for applications where their properties coupled with extended lengths will enable new technology developments². For example, ultralong nanotubes can be spun into fibres that are more than an order of magnitude stronger than any current structural material, allowing revolutionary advances in lightweight, high-strength applications³. Long metallic nanotubes will enable new types of micro-electromechanical systems such as micro-electric motors, and can also act as a nanoconducting cable for wiring micro-electronic devices⁴. Here we report the synthesis of 4-cm-long individual single-wall carbon nanotubes (SWNTs) at a high growth rate of 11 μm s⁻¹ by catalytic chemical vapour deposition. Our results suggest the possibility of growing SWNTs continuously without any apparent length limitation.

We present results of temperature and magnetic field dependent resistivity ρ(H,T) and bulk magnetization M(H,T) measurements on post‐annealed La_0.7Ca_0.3MnO₃ thin films that were grown via pulsed‐laser deposition. Both the resistivity and the anomalously large negative magnetoresistance peak near the ferromagnetic ordering temperature (T_c=250 K), with Δρ/ρ₀=−85% at 50 kOe. A clear correlation is found between ρ and M that is described by the phenomenological expression ρ(H,T)∝exp[−M(H,T)/M₀]. This correlation reflects the important interplay between transport and magnetism in this system, and suggests that the transport below T_c involves polaron hopping.