2D nature of magnetic states at SnO2 surfaces: a combined experimental and theoretical study.

For undoped SnO2, room temperature ferromagnetism could be seen uniquely in 2-dimensional configurations, particularly in ultra-thin films (whose thickness is ideally below 100 nm). Both bulk samples and nano-powders of pristine SnO2 are diamagnetic, indicating that a 2D surface is a key point in shaping up the magnetic properties in SnO2. As a complement to our experiments, we have performed a series of quantum-mechanical calculations for the bulk rutile-structure SnO2 as well as its (001) and (101) surfaces. The calculations included several atomic configurations with and without vacancies in/under the studied surfaces. The stability of the non-magnetic ground state of rutile SnO2 bulk was cross-checked and confirmed by its phonon spectrum computed within the harmonic approximation. Regarding the surfaces, the bulk-like (001) surface containing Sn vacancies has turned out to be ferromagnetic, while the shift of Sn vacancies under the surface resulted in a more complex ferrimagnetic state. The bulk-like (001) surface without vacancies and that with the O vacancies are predicted to be non-magnetic. Regarding the (101) surfaces, those terminated by a single layer of oxygen atoms and those terminated by tin atoms are non-magnetic, while a surface terminated by two layers of oxygen has turned out to be ferromagnetic.

Mesoporous silica with fibrous morphology: a multifunctional core-shell platform for biomedical applications.

Multifunctional mesoporous silica nanocomposites are attractive carriers for targeted drug delivery in nanomedicine. Although promising developments have been made in the fabrication of multifunctional mesoporous silica nanocomposites, the design and mass production of novel multifunctional carriers are still challenging. This paper reports the facile one-pot fabrication of a multifunctional inorganic composite composed of superparamagnetic Fe3O4 nanoparticles and coated dye-functionalized mesoporous silica with a high specific surface area. The resulting composite particles had a tunable particle size, special open pore channels with high specific surface area, which is quite favorable for drug loading and release properties, as well as luminescent and superparamagnetic properties suitable for targeted drug delivery and tracking. This composite exhibited low toxicity, suggesting potential biomedical applications.

Toxicity and T2-Weighted Magnetic Resonance Imaging Potentials of Holmium Oxide Nanoparticles.

In recent years, paramagnetic nanoparticles (NPs) have been widely used for magnetic resonance imaging (MRI). This paper reports the fabrication and toxicity evaluation of polyethylene glycol (PEG)-functionalized holmium oxide (Ho2O3) NPs for potential T2-weighted MRI applications. Various characterization techniques were used to examine the morphology, structure and chemical properties of the prepared PEG-Ho2O3 NPs. MRI relaxivity measurements revealed that PEG-Ho2O3 NPs could generate a strong negative contrast in T2-weighted MRI. The pilot cytotoxicity experiments showed that the prepared PEG-Ho2O3 NPs are biocompatible at concentrations less than 16 µg/mL. Overall, the prepared PEG-Ho2O3 NPs have potential applications for T2-weighted MRI imaging.

Thickness Dependence Magnetization in Laser Ablated Ni-Cu-Zn Ferrite Nanostructured Thin Films.

Ni0.5Cu0.3Zn0.2Fe2O4 thin films with thickness ranging from 25 nm to 500 nm were grown on Si substrate using pulsed laser deposition technique and their structural and magnetic properties were investigated. From the atomic force microscopy (AFM) analysis, it is observed that the film roughness (Ra) depends strongly on the thickness of the fabricated film. The magnetizations of the thin films were found to decrease when the film thickness increases. The thinner films showed a larger magnetization than the thick films. All the films showed a blocking temperature indicating their superparamagnetic behavior.

Magnetism in V-doped ZnO thin films.

Ferromagnetism at room temperature, along with a spin-glass-like behaviour at low temperatures, has been observed in laser ablated V-doped ZnO thin films. It is found that V atoms were well substituted for Zn atoms and resulted in a very uniform distribution among the ZnO matrices.

Room temperature ferromagnetism with large magnetic moment at low field in rare-earth-doped BiFeO3 thin films.

Thin films of rare earth (RE)-doped BiFeO3 (where RE=Sm, Ho, Pr and Nd) were grown on LaAlO3 substrates by using the pulsed laser deposition technique. All the films show a single phase of rhombohedral structure with space group R3c. The saturated magnetization in the Ho- and Sm-doped films is much larger than the values reported in the literature, and is observed at quite a low field of 0.2 T. For Ho and Sm doping, the magnetization increases as the film becomes thinner, suggesting that the observed magnetism is mostly due to a surface effect. In the case of Nd doping, even though the thin film has a large magnetic moment, the mechanism seems to be different.

The origin of magnetism in transition metal-doped ZrO2 thin films: experiment and theory.

We have investigated the magnetic properties of Fe/Co/Ni-doped ZrO2 laser ablated thin films in comparison with the known results of Mn-doped ZrO2, which is thought to be a promising material for spintronics applications. It is found that doping with a transition metal can induce room temperature ferromagnetism in 'fake' diamond. Theoretical analysis based on density functional theory confirms the experimental measurements, by revealing that the magnetic moments of Mn- and Ni-doped ZrO2 thin films are much larger than that of Fe- or Co-doped ZrO2 thin films. Most importantly, our calculations confirm that Mn- and Ni-doped ZrO2 show a ferromagnetic ground state in comparison to Co- and Fe-doped ZrO2, which favor an antiferromagnetic ground state.