Unique magnetic properties and magnetization reversal process of CoFe2O4 nanotubes fabricated by electrospinningElectronic supplementary information (ESI) available: EDX spectrum and mappings, statistical analysis of nanoparticle size. See DOI: 10.1039/c2nr30487b

CoFe 2 O 4 nanotubes have been directly fabricated by single-capillary spinneret electrospinning. The external diameter of the CoFe 2 O 4 nanotubes ranges from 60 nm to 160 nm. The morphology and structure characterizations show that individual CoFe 2 O 4 nanotubes are made of CoFe 2 O 4 nanocrystals stacking along the nanotubes with no preferred growth directions and these individual nanocrystals are single crystal with a cubic spinel structure. Each nanocrystal was shown to be a single magnetic domain. The magnetic measurements show that the coercivity ( H c ) of the CoFe 2 O 4 nanotubes decreases from 10 400 Oe at 5 K to 300 Oe at 360 K. The CoFe 2 O 4 nanotubes have a spin reorientation (SR) at 5 K, which is different from CoFe 2 O 4 nanorods and nanoparticles. Based on the observed morphology and crystal structure, a micromagnetic model, "chain-of-rings", is developed to interpret the magnetic behavior of the CoFe 2 O 4 nanotubes. The theoretical coercivity (534 Oe) is in good agreement with the experimental results (509 Oe). It is believed that our work should open a new route to prepare various magnetic ferrite nanotubes and is significant for expanding the application of CoFe 2 O 4 into the new fields. CoFe 2 O 4 nanotubes have showed spin-reorientation phenomenon at low temperature, and their magnetization reversal process has also been investigated.