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Diluted magnetic semiconductor based on Ni-doped TiO 2 has been synthesized by hydrothermal process and effect of Ni doping on structure, morphology and magnetic studies were investigated. X-ray Rietveld analysis confirmed that all the samples were TiO 2 anatase structure without having any impurity phase. The lattice parameter and cell volume increased in Ni-doped TiO 2 nanotubes. TEM micrograph reveals clearly the formation of TiO 2 nanotubes with diameter of ∼8 nm. Magnetic properties studies were carried out by using vibrating sample magnetometer at room temperature and ferromagnetism was observed in both pure and Ni-doped TiO 2 nanotubes. The bound magnetic polarons formed by Ni ions and the oxygen vacancy may be responsible for the increased magnetic moment in Ni-doped TiO 2 nanotubes. These findings provide a better understanding for the mechanisms of Ni doped TiO 2 nanotubes ferromagnetism at room temperature.

We fabricated Gd-doped Y3Fe5O12 (YIG) nanoparticles by a modified sol–gel method. We investigated the effects of isovalent Gd3+-ion substitution on the structural and magnetic properties of Y3−xGdxFe5O12 (0 ≤ x ≤ 3) nanoparticles. Isovalent Gd3+-ion substitution for Y3+ leads to lattice expansion and change in the Fe(a)–O–Fe(d) bond angle. The X-ray photoemission spectroscopy and Mossbauer measurements revealed a high-spin state of Fe3+. The Mossbauer analysis showed an increase in the Fe(d)3+/Fe(a)3+ ratio, indicating a relocation of Y3+ ions at the dodecahedral sites and Fe3+ ions at the octahedral sites. The magnetic properties could be explained in terms of magnetic-structural evolution with increasing Gd3+ content. The field dependence of magnetization indicated a clear decrease of the magnetization while the magnetic anisotropy first decreases and then increases with the increase of Gd3+ content. These Gd3+-ion-substituted nanocrystalline garnet ferrites are suitable for use in a variety of magneto-optical applications.

We fabricated single-crystalline, Gd-doped BiFeO3 (BFO) nanowires using a hydrothermal technique. X-ray diffraction (XRD) data combined with their Rietveld refinements and high-resolution transmission electron microscopy (HRTEM) revealed pure single-phase crystalline Bi1−xGdxFeO3 (x = 0, 0.05, 0.10) nanowires of 40–60 nm diameter and their structural transformation from the rhombohedral R3c (for x = 0 and 0.05) to the orthorhombic Pn21a crystal structure (for x = 0.10). The addition of Gd3+ ions to the pure-phase BFO leads to remarkable changes in the structural and magnetic properties, and these effects are caused by differences in the ionic-radii and magnetic moment between the Bi3+ and Gd3+ ions. According to the observed magnetization-field (M–H) and magnetization-temperature (M–T) curves, with increasing Gd3+ concentration, the saturation magnetization (MS), squareness (Mr/MS), coercivity (HC), exchange-bias field (HEB) and magnetocrystalline anisotropy (K) increased markedly, by MS = 1.26 emu g−1 (640%), Mr/MS = 0.19 (20.5%), HC = 7788 Oe (4560%), HEB = 501 Oe (880%) and K = 1.62 × 105 erg cm−3 (3500%), for x = 0.10 relative to the data for x = 0. In such Gd-doped BFO nanowire samples, spin-canted Dzyaloshinskii–Moriya interaction, remarkable enhancements in the magnetocrystalline anisotropy as well as uncompensated surface ferromagnetic spin states in the antiferromagnetic core regions were also found. Such remarkable enhancements in Gd-doped BFO nanowires might offer a variety of spintronic applications.

We investigated the static and dynamic aspects of the magnetic properties for single phase nanocrystalline BiFeO 3 with average crystallite size of 35 nm. The frequency dependence of the peak is observed in the real part of ac susceptibility χ′ ac vs T measurement and described well by the Vogel-Fulcher law as well as the power law. These analyses indicated the existence of cluster glass state with significant interaction among the spin clusters and results in cluster-glass like cooperative freezing at low temperature. The influence of temperature and magnetic field cooling on the exchange bias effect is investigated. A training effect is also observed. We have reported a significantly high ZFC & FC exchange bias of 200 Oe & 450 Oe at 300 K and 900 Oe & 2100 Oe at 5 K. The obtained results are interpreted in the framework of core-shell model, where the core of the BFO nanoparticles shows antiferromagnetic behavior and surrounded by CG-like ferromagnetic (FM) shell associated to uncompensated surface spins.

Co 2+ -doped Y 2 O 3 nanorods of 70–100 nm diameters and 0.3–2 µm lengths with different compositions ( x =0.00, 0.04, 0.08) in Y 2− x Co x O 3 were synthesized by an easy hydrothermal method. The X-ray diffraction, Raman spectra, X-ray photoelectron spectroscopy and transmission electron microscopy (TEM) results indicated the formation of a pure cubic phase structure of Y 2 O 3 doped with Co 2+ ions without any secondary phase formation. The TEM analysis indicated that the nanorods were grown along the [100] axis. The pure Y 2 O 3 nanorods showed diamagnetism whereas the Co 2+ -doped ones exhibited room-temperature ferromagnetism. The existence of such room-temperature ferromagnetic behavior in Co 2+ -doped Y 2 O 3 nanorods is due mainly to the existence of oxygen vacancies originating after the doping of transition metal ions in the Y 2 O 3 host lattice. Oxygen vacancies act as defect centers in the bound magnetic polaron model to account for this dilute magnetic oxide of medium band gap with low transition-metal-ion concentration. The presence of defect-related oxygen vacancies was further confirmed by photoluminescence spectra analysis of our studied materials.

Cobalt-doped Gd2O3 (Gd2−xCoxO3, 0≤x≤0.06) nanorods of about 100 nm diameter and 2 µm length were synthesized using a simple hydrothermal method. XRD, Raman, XPS, and TEM measurements showed the samples to have a single cubic phase structure of Gd2O3 doped with Co2+ cations, without any cobalt clusters. All the samples showed paramagnetism at room temperature as well as at 5 K. The samples’ high magnetization values at 5 K were due to reduction of the thermal randomization of the magnetic spins. The Curie–Weiss fitting of the magnetic data reflected antiferromagnetism along with paramagnetism due to the exchange interactions of Gd3+ via O2− ions and coupling between Co2+–Co2+ pairs.

We have investigated the effect of sintering temperature on the densification behaviour, grain size, structural and dielectric properties of BaTiO3 ceramics, prepared by high energy ball milling method. The Powder x-ray diffraction reveals the tetragonal structure with space group P4mm for all the samples. The samples were sintered at four different temperatures, (T = 900°C, 1000°C, 1100°C, 1200°C and 1300°C). Density increased with increasing sintering temperature, reaching up to 97% at 1300°C. A grain growth was observed with increasing sintering temperature. Impedance analyses of the sintered samples at various temperatures were performed. Increase in dielectric constant and Curie temperature is observed with increasing sintering temperature.

Monodisperse indium oxide (In 2 O 3 ) nanoparticles (NPs) with the average diameter of 11 nm were prepared by a solvothermal method. The In 2 O 3 NPs were characterized by X-ray diffraction, Raman and transmission electron microscopy. The intrinsic nature of ferromagnetism in In 2 O 3 NPs has been established with the experimental observation of magnetic hysteresis loop. Photoluminescence and UV–visible studies were employed to evidence the presence of oxygen vacancies and revealed that the oxygen vacancies contribute to the ferromagnetism. The origin of ferromagnetism in In 2 O 3 NPs may be due to exchange interactions among localized electron spin moments resulting from oxygen vacancies.

Implant placement in the maxillary anterior region has always been challenging for the implantologists. Different levels of gingival display, along with the uncertainty of soft- and hard-tissue changes postextraction make things highly predictable in this part of the alveolar ridges. This difficulty is augmented by the patient's desire to have teeth in this esthetic zone immediately. Researchers have devised certain techniques to address this issue and one such method of an immediate, highly esthetic rehabilitation is called the socket shield technique (SST). The use of cortical engagement in this region along with SST gives the operator an opportunity to immediately load the prosthesis with optimal esthetic outcomes. Another challenging issue secondary to implant therapy is peri-implant infections, including the more common peri-implantitis. The presence of rough implant surfaces, when exposed to the oral environment, leads to the formation of a kind of nidus, which, further, feeds soft- and hard-tissue loss. The presence of a periapical pathology from previous dentition may also infect the implant surface. An attempt was made in this case to utilize the SST along with the provision of smooth-surfaced dental implants, stabilized with cortical engagement, for the replacement of missing maxillary anterior teeth.

We report the room-temperature ferromagnetism in Cr-doped TiO 2 nanorods (NRs) synthesized via the hydrothermal method followed by annealing at 700 °C. The transmission electron microscopy showed that the diameter of the NRs is between 40 and 70 nm. X-ray diffraction, XPS and Raman technique are used to confirm the absence of magnetic contaminations of metallic Cr clusters or any other phases. To test the oxygen vacancy related ferromagnetism, annealing in oxygen, air and argon are performed. With the changing of annealing atmosphere from oxygen to argon, the saturation magnetization ( M s ) of NRs increases. These results strongly prove that the oxygen vacancies play an important role in inducing the ferromagnetism. The shifting and broadening of the most intense E g (1) mode at 144 cm −1 observed by Raman spectroscopy further confirms that the origin of the ferromagnetism in NRs is due to the oxygen vacancies.

A series of Ti1−xFexO2−δ (0 ≤ x ≤ 0.03) nanoparticles (NPs) were synthesized by sol–gel route. The NPs had a size distribution in the range of 15–40 nm and were identified as the anatase TiO2 by X-ray diffraction (XRD) and Raman analysis. XRD, selected area electron diffraction, Raman and Mossbauer analysis ruled out the signature of Fe-cluster or any other oxides of Fe. The redshifting of the band edge emission peak observed in UV–vis absorption studies further confirmed the doping of Fe ions in the TiO2 lattice. Raman studies show the shifting and broadening in Eg(1) and Eg(3) modes with Fe doping. It suggested that the activation of ferromagnetism with increasing Fe doping concentration was related to the oxygen vacancy defects. The presence of such defects was further confirmed from electron paramagnetic resonance (EPR) measurements. The observed ferromagnetism is interpreted in terms of bound magnetic polaron (BMP) model.

The Cu-doped hydrogen titanate nanorods are synthesized via a hydrothermal reaction and converted into Cu-doped TiO2(B) and anatase phases by calcinations. X-ray diffraction (XRD), Fourier transform infrared (FTIR) and selected area electron diffraction (SAED) pattern do not show the presence of any other phases and thus confirmed the intrinsic ferromagnetic behavior rather than it arising from metallic clusters. The blue shifting in absorption edge and increase in photoluminescence (PL) intensity from Cu-doped hydrogen titanate to anatase phase are strongly correlated with concentration of oxygen vacancies and defect formation. The higher concentration of oxygen vacancies and/or structural defects leads to the coalescence of ferromagnetic domains, which corroborates to the observed higher magnetization value of Cu-doped anatase phase compared to other phases.

Nanotubes of TiO2(B) phase doped with 5 at.% of vanadium (V) have been synthesized by a hydrothermal method, followed by calcination at 300 °C in air and argon atmosphere, respectively. These nanotubes exhibit ferromagnetic character with clear hysteresis loop at room-temperature. X-ray diffraction and Fourier transform infrared spectroscopy confirm that the ferromagnetic behavior is intrinsic to the material and not due to other phases and/or metallic clusters. The photoluminescence and hysteresis loop characteristics are found to be dependent on calcination conditions, and implicate the role of oxygen vacancies. Existence of higher oxygen vacancies in V-doped TiO2(B) nanotubes synthesized in argon than the air atmosphere is supported by the room-temperature photoluminescence spectra. The enhanced ferromagnetic behavior observed in V-doped TiO2(B) nanotubes synthesized in argon than the air atmosphere is explained in terms of bound magnetic polaron (BMP) model.

Mn-doped TiO2 nanorods which showed room temperature ferromagnetic (RTFM) behavior have been synthesized by a hydrothermal method. Analysis of X-ray diffraction and Raman spectral data reveal the formation of anatase phase without any impurity phase. From the hysteresis loop measurements, it is possible to estimate the two parameters, magnetization (MS) and coercivity (HC) which are 33 memu/g and 89 Oe respectively, for 5 at% Mn-doped TiO2. The two parameters (MS, HC) are strongly dependent on the Mn doping concentration. The origin of the RTFM is understood in terms of the concentration of oxygen vacancies and/or defects which is created by Mn doping.

Cu-doped TiO2 anatase nanorods are obtained by annealing the hydrothermally synthesized Cu-doped titanate nanotubes precursor at temperatures 500 °C in different atmosphere (oxygen, air and argon). TEM image of the nanorods confirmed that the nanorods are randomly oriented with an average length of 100 nm and a mean diameter of 15–25 nm. X-ray diffraction ruled out the formation of either metallic Cu or copper oxide cluster and confirmed the intrinsic ferromagnetic nature. The photoluminescence (PL) spectrum analysis revealed that the ferromagnetism is due to the defects. The ferromagnetic order of Cu-doped TiO 2 anatase nanorods is found to be greater in argon atmosphere than air. In the case of oxygen annealed sample least ferromagnetic ordering is found due to quenching of oxygen vacancies defects. The observed sequence of reduction in ferromagnetism shows a close inter-relationship with the behavior of oxygen vacancies..

Photoluminescence of Rhodamine B dye solution containing nanostructures of titanium dioxide (nanoparticles, nanorods, and nanotubes) was investigated at various optical excitation intensities. The stimulated emission was observed owing to multiple scattering of photons in the dye solution. The threshold intensity, emission wavelength, and profile of stimulated emission are different for different nanostructures. Single and double emission peaks were observed, respectively, at low (10−3 M) and high (10−2 M) dye concentrations. The stimulated emission characteristics with nanostructures dispersed in dye solution are attributed to the nonresonant scattering.

Fe-doped TiO2(B) and anatase phases were synthesized at different thermal treatment conditions using Fe-doped hydrogen titanate nanorods as a precursor. X-ray diffraction, Raman and Mössbauer studies ruled out the formation of secondary phase of either metallic Fe or iron oxide cluster in the samples and confirmed the ferromagnetism have originated from the defects. Mössbauer spectroscopy studies show a doublet and measured isomer shifts support the high spin Fe3+ charge state occupying the Ti4+ sites with associated changes in local lattice environment. The magnetization at room-temperature of the TiO2(B) sample is 0.020 emu/g whereas that of anatase sample is 0.015 emu/g. The decrease of magnetization with the structural phase transformation from TiO2(B) to anatase is attributed to the reduction in number of defects (oxygen vacancy) during the transformation process. Existence of these defects was further supported by the photoluminescence measurements.