SEM micrographs for the nanowires with a typical diameter of (a) 51 nm, (b) 62 nm, (c) 86 nm, and (d) 104 nm. (e) HRTEM image of a portion of the 104-nm-diameter nanowires. Inset is the corresponding SAED pattern. (f) Diameter distribution histograms (obtained from SEM images) for the as-synthesized four series of nanowires.
XRD pattern and Rietveld refinement result for the 51 nm nanowires at room temperature. The experimental data are shown as red crosses; the global fitting profile and the difference curve are shown as black and blue solid lines, respectively. The calculated reflection positions are indicated by green short ticks. Some weak diffraction peaks (e.g., the peak at 24°) that do not belong to the phase with space group come from the reflection of symmetry. These weak diffraction peaks are indexed when the space group is adopted in refinement. The inset presents a structural sketch of with space group.
Room-temperature structural parameters for the nanowires (closed symbols), including lattice parameters , , and , monoclinic angle , Co–O bond length , Co–O–Co bond angle , and the degree of JT distortion D%. For comparison, the structural parameters for the bulk are also shown as the open symbols.
FC magnetization of the nanowires and bulk measured in an applied field .
Magnetic field dependence of magnetization for the nanowires at 5 K.
(a) Saturated magnetization and (b) Curie temperature and onset FM temperature for the nanowires (closed symbols) and the bulk (open symbols); the dashed lines are the guide for eyes.
(a) Effective PM magnetic moment and (b) effective total spin as a function of average Co–O bond length ; the solid lines are the linear fittings.
Temperature dependence of the degree of JT distortion D% for the 51 nm nanowires and the bulk. The black dots are the data of single crystal reported by Maris et al. (Ref. 20).
Space groups, lattice parameters, atomic positions, isotropic thermal factor , and fitting factors (, , and ) for the bulk and 51 nm nanowires at room temperature.
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