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We present a detailed study of the electron magnetic resonance (EMR) properties of Ni nanoparticles (NPs) placed in the bundles of single-walled carbon nanotubes produced by arc discharge with Ni catalyst. The behavior of EMR signals has been investigated in the 10–300 K temperature range for the initial powderlike materials and those diluted in a nonmagnetic matrix. The magnetic response evolves between two modes, ferromagnetic and superparamagnetic, depending on both the temperature and distribution of Ni nanoparticles in the sample. The behavior of EMR spectra shows that the initial materials retain the ferromagnetic character of the NP ensemble even at room temperature. This is most likely due to dipole-dipole interactions and macroscopic demagnetizing fields stemming from powderlike composition of the samples. For the diluted materials, the actual superparamagnetic signal is observed at room temperature. As temperature is reduced, the behavior of the EMR parameters reflects a gradual transition from free rotated magnetic moments of NPs to those ordered along the “easy” magnetic axes (blocked state). In the 300–130 K temperature range, anomalous temperature dependence of the resonance magnetic field Hres was observed. It is examined in terms of competition between the single-particle anisotropy energy and dipole interactions between the Ni nanoparticles. Finally, a transition to a blocked state occurs at blocking temperature estimated as Tb≈40 K. At lower temperatures, both the dense and diluted samples behave identically. [ABSTRACT FROM AUTHOR]

Doping of diamond by substitutional insertion of metallic species or production of diamond/metals nanocomposite layers has been obtained by a hybrid chemical vapor deposition based technique. The potential of such an approach makes it possible to obtain a wide class of purposely designed diamond-based structures characterized by specific properties of charge transport. Reflection high-energy electron diffraction, scanning electron microscopy and x-ray dispersive spectrometry have been used to study the structural and compositional characteristics of some Nd-, W- and Ti-containing diamond films. The peculiar electrical properties conferred to the host diamond layers by the insertion of various metals have been investigated in the range of 25-500 K by performing Hall effect and conductivity measurements. The mechanism of charge transport and the electrical properties of these materials are found to be mainly governed by organization of the metallic species, which can be in different forms, such as dispersion at the atomic scale and the distribution of isolated clusters or aggregates localized at grain boundaries. Depending on the microstructure, the resulting materials can behave as p-type semiconductors, characterized by resistivity values as low as 3.3 × 10[sup -3] Ω cm and high values of Hall mobility, or show metal-like conduction, with resistivity as low as 2.2 × 10[sup -1] Ω cm. The insertion of metallic species does not perturb the crystalline quality of the host diamond matrix and, consequently, the layers produced combine the outstanding properties of diamond with electrical behavior that can be modulated for specific applications. [ABSTRACT FROM AUTHOR]

Deals with a study which investigated the structure of the transition layers formed at the interface between titanium substrate and diamond films, using the reflection high-energy electron diffraction (RHEED) technique. Information on the RHEED technique; Methodology of the study; Results and discussion.

Focuses on a study which monitored the structural modifications induced by pulsed laser irradiation in the surface layers of glassy carbon. Experimental procedures; Patterns of diffraction in glassy carbon; Description of the Raman spectra of glassy carbon.