Sodium vanadium oxide Na 2 V 6 O 16 ·3H 2 O nanobelts and nanorings: A new room-temperature ferromagnetic semiconductor

We report the first observation of nanorings coiled by nanobelts in our synthesized Na2V6O16·3H2O (Barnesite) sample by a simple and novel cost-effective low-temperature hydrothermal method, and also find room temperature ferromagnetism in the product for the first time. The Na2V6O16·3H2O samples are characterized by XRD, SEM and XPS to ascertain their structure, morphology and composition. They exhibit ferromagnetic properties with coercivity of 400 Oe at 300 K observed from a hysteresis loop. The XPS spectra, and the hysteresis loops of the sample before and after annealing both demonstrate that the origin of ferromagnetism in the Na2V6O16·3H2O product is attributed to the introduction of oxygen vacancies. The polarization-induced self-coiling of in situ formed Na2V6O16·3H2O nanobelts is responsible for the formation of the perfectly circular nanoring geometry and it may be useful to investigate polar surface-induced growth processes, fundamental physics phenomena, and the design for nanoscale devices.