Thermal stability and the magnetic properties of hybrid vanadium oxide-tetradecylamine nanotubes

SALETA; LOPEZ; GRANADA; TROIANI; SANCHEZ; MALTA; TORRESI

JOURNAL OF APPLIED PHYSICS

AMER INST PHYSICS

Lugar: New York; Año: 2012 p. 1 - 7

0021-8979

Vanadium oxide nanotubes (NTs) were synthesized by the sol-gel method followed by a long-termhydrothermal treatment. The obtained nanotubes have a multiwall structure, and 70% of vanadiumions are in the V4þ state. This percentage was derived by evaluating three components of themagnetic susceptibility; namely, (i) the paramagnetic Curie-Weiss behavior, (ii) antiferromagneticdimers, and (iii) magnetic trimers. The as-made NTs were annealed in situ in the cavity of theelectron paramagnetic resonance (EPR) spectrometer. The line shape changes irreversibly at 390 K,and the EPR susceptibility presents an anomaly at 425 K. These changes are interpreted as a partialoxidation of the V4þ ions and consequently a decrease in the concentration of the magnetic species.The quantification of the V4þ ions of the annealed NTs reveals a diminution to 39% of V4þ, aweakening of the Curie-Weiss and antiferromagnetic dimers contributions, and the suppression ofmagnetic trimers. Vibrational studies confirm the decrease of V4þ amount. VC 2012 AmericanInstitute of Physics.