TY - JOUR
T1 - Occurrence and stability of ferromagnetism in chemically synthesized cobalt doped TiO 2
AU - Reddy, K. M.
AU - Punnoose, A.
PY - 2007/11
Y1 - 2007/11
N2 - We report the development of ferromagnetism in ∼30 nm sized well-characterized Ti 1-xCo xO 2 powders with x = 0.00015-0.006 and its absence for x > 0.006. In addition, these studies show the effect of Co doping on the structural stability and anatase to rutile phase transformation. X-ray diffraction data of samples synthesized by a wet chemical method and annealed at 450 °C indicate a limited solubility of ∼1.2% for Co in the anatase TiO 2 matrix, and with further increase, the CoTiO 3 phase is formed along with increased presence of rutile TiO 2. The bandgap (∼3.23 eV) of the anatase TiO 2 remained almost unchanged for x < 0.006, but decreased rapidly for x < 0.006 approaching 2.8 eV for x = 0.03. The magnetic data from Ti 1-xCo xO 2 samples with x = 0.006 showed a coercivity H c ∼ 150 Oe and a weak magnetic moment of 0.2 μ B/ion at 300 K. The ferromagnetism of Ti 0.994Co 0.006O 2 with open hysteresis loops continue up to a high superparamagnetic blocking temperature T B ∼ 675 K, above which a superparamagnetic behavior was observed. Systematic changes in the structural, magnetic and optical properties suggest that Co doping is an excellent method to tailor the physical properties of TiO 2 nanoparticles.
AB - We report the development of ferromagnetism in ∼30 nm sized well-characterized Ti 1-xCo xO 2 powders with x = 0.00015-0.006 and its absence for x > 0.006. In addition, these studies show the effect of Co doping on the structural stability and anatase to rutile phase transformation. X-ray diffraction data of samples synthesized by a wet chemical method and annealed at 450 °C indicate a limited solubility of ∼1.2% for Co in the anatase TiO 2 matrix, and with further increase, the CoTiO 3 phase is formed along with increased presence of rutile TiO 2. The bandgap (∼3.23 eV) of the anatase TiO 2 remained almost unchanged for x < 0.006, but decreased rapidly for x < 0.006 approaching 2.8 eV for x = 0.03. The magnetic data from Ti 1-xCo xO 2 samples with x = 0.006 showed a coercivity H c ∼ 150 Oe and a weak magnetic moment of 0.2 μ B/ion at 300 K. The ferromagnetism of Ti 0.994Co 0.006O 2 with open hysteresis loops continue up to a high superparamagnetic blocking temperature T B ∼ 675 K, above which a superparamagnetic behavior was observed. Systematic changes in the structural, magnetic and optical properties suggest that Co doping is an excellent method to tailor the physical properties of TiO 2 nanoparticles.
UR - https://www.scopus.com/pages/publications/34548145835
U2 - 10.1007/s10854-007-9127-6
DO - 10.1007/s10854-007-9127-6
M3 - Article
AN - SCOPUS:34548145835
SN - 0957-4522
VL - 18
SP - 1137
EP - 1142
JO - Journal of Materials Science: Materials in Electronics
JF - Journal of Materials Science: Materials in Electronics
IS - 11
ER -