Figure 6
(a) EPR spectra of the as-grown and post-annealed Fe3O4 nanotubes measured at 275 K and 105 K (at 9.3 GHz). The external magnetic field is perpendicular to the tube length direction. (b) The variations of the resonance filed Hr and the corresponding FMR linewidth deduced from the EPR spectra as a function of temperature for the as-grown Fe3O4 nanotubes. (c) The resonance field as a function of temperature for the post-annealed Fe3O4 nanotubes, with the external magnetic fields parallel and perpendicular to the tube length direction. The upper inset is the FMR linewidth as a function of temperature. (d) Angular dependences of the normalized resonance fields at 275 K and 105 K.
