• Journal of the Korean Magnetics Society
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• v.16 no.4
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• pp.206-210
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• 2006

A room-temperature ferromagnetism has been observed for oxygen-deficient rutile and anatase $TiO_{2-{\delta}}$ films. XPS data revealed the existence of $Ti^{3+}$ ions, for compensating the charge imbalance caused by oxygen vacancies in the film. The observed ferromagnetism is attributable to the spin ($3d^1$) alignment of the $Ti^{3+}$ ions. Such spin alignment can happen through magnetic polaron formed by trapped electron in oxygen vacancy and magnetic $Ti^{3+}$ ions around it.

• Journal of the Korean Magnetics Society
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• v.16 no.3
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• pp.168-172
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• 2006

We studied the magnetic and the related electronic properties of Ni-doped rutile $TiO_{2-{\delta}}$ films (including oxygen deficiency $\delta$) prepared using a sol-gel method. A room-temperature ferromagnetism was observed in the $TiO_{2-{\delta}}$ : Ni films with the saturation magnetization ($M_S$) decreasing with increasing Ni doping and remaining constant above 6 at% Ni doping. The observed ferromagnetism below 6 at% Ni doping is interpreted as due to magnetic polaron formed by a trapped electron in oxygen vacancy and magnetic impurity ions around it. For small Ni doping, $M_S$ up to $3.7{\mu}B/Ni$ was obtained. The ferromagnetism for Ni doping above 6 at% is interpreted as due to the existence of Ni clusters that can explain the p-n conductivity transition observed by Hall effect measurements.

• Journal of the Korean Chemical Society
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• v.53 no.1
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• pp.42-50
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• 2009

The dielectric-spectroscopic and ac conductivity studies firstly carried out on layered manganese doped Sodium Lithium Trititanates ($Na_{1.9}Li_{0.1}Ti_3O_7$). The dependence of loss tangent (Tan$\delta$), relative permittivity ($\varepsilon_r$) and ac conductivity ($\sigma_{ac}$) in temperature range 373-723K and frequency range 100Hz-1MHz studied on doped derivatives. Various conduction mechanisms are involved during temperature range of study like electronic hopping conduction in lowest temperature region, for MSLT-1 and MSLT-2. The hindered interlayer ionic conduction exists with electronic hopping conduction for MSLT-3. The associated interlayer ionic conduction exists in mid temperature region for all doped derivatives. In highest temperature region modified interlayer ionic conduction along with the polaronic conduction, exist for MSLT-1, MSLT-2, and only modified interlayer ionic conduction for MSLT-3. The loss tangent (Tan$\delta$) in manganese-doped derivatives of layered $Na_{1.9}Li_{0.1}Ti_3O_7$ ceramic may be due to contribution of electric conduction, dipole orientation, and space charge polarization. The corresponding increase in the values of relative permittivity may be due to increase in number of dipoles in the interlayer space while the corresponding decrease in the values of relative permittivity may be due to the increase in the leakage current due to the higher doping.