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Electrodeposition of cobalt on monolayer graphene synthesized by chemical vapor deposition produces Co–CoO/graphene composite structures, which is accompanied by increases in the electrical resistance and magnetoresistance. We show that the observed magnetoresistance effect is caused by two competing contributions: negative (NMR) and positive (PMR) magnetoresistance. In weak magnetic fields, the NMR is described by quantum localization correction to the Drude model of conductivity in graphene. The enhancement of PMR observed in strong magnetic fields is related to the Lorentz mechanism in Co–CoO particles.

The thermal evolution of defects inside and beyond the implantation layer in Si wafer exposed to the irradiation with 25 keV C+, N+ and Ar+ ions with different doses has been investigated by positron beam measurements. Two types of defects were detected: the small cavities and divacancies in the implanted layer which thickness corresponding to the projectile range. Cavities were only present for dose 2*1016 and were not observed for 2*1014 and 2*1015 ions/cm2. For the dose of 2*1016 ions/cm2 the defects were detected also beyond the implantation layer indicating the presence of the long range effect. Obtained results indicate on influence of ion type and dose on defect distribution and its thermal evolution beyond the implanted layer. The recovery process was similar for Ar+ and N+ but differ for C+ ion implantation.

We present an experimental study of the longitudinal and transverse relaxation of ensembles of negatively charged nitrogen-vacancy (NV−) centers in a diamond monocrystal prepared by 1.8 MeV proton implantation. The focused proton beam was used to introduce vacancies at a 20 µµm depth layer. Applied doses were in the range of 1.5×1013 to 1.5×1017 ions/cm2. The samples were subsequently annealed in vacuum which resulted in a migration of vacancies and their association with the nitrogen present in the diamond matrix. The proton implantation technique proved versatile to control production of nitrogen-vacancy color centers in thin films.

Experiments searching for the neutrinoless double beta decay in $$^{76}$$ 76 Ge are currently achieving the lowest background level and, in connection with the excellent energy resolution of germanium detectors, they exhibit the best discovery potential for the decay. Expansion to a ton scale of the active target mass is presently considered – in this case on-site production of the detectors may be an option. In this paper we describe the fabrication and characterization procedures of a prototype detector with a small p+ contact, which enhances the abilities of the pulse shape discrimination – one of the most important tools for background reduction. Simulations of the shapes of pulses from the detector were carried out and tuned, taking the advantage of the fact that all the parameters of the Ge crystal, cryostat and of the spectroscopic chain were known. As a result, the pulse shape analyses performed on the simulated and measured data agree very well. The worked out method allows to optimize geometry and crystal parameters in terms of pulse shape analysis efficiency, before the actual production of the detectors.

In this paper, the structural, microstructural, electrical and magnetic properties of an Mn2CoO4 spinel synthesized by means of EDTA gel processes are reported. The Rietveld refinement analysis of high-temperature X-ray diffraction (HT-XRD) data revealed the formation of a tetragonal Mn2CoO4 phase. This phase undergoes a structural change into a cubic phase at elevated temperatures, and this process is associated with a change in lattice parameters. The afore-mentioned phase transition was also investigated via high-temperature Raman spectroscopy. Temperature-dependent magnetization data revealed changes in the magnetic ordering temperature, which had been caused by the formation of antiferromagnetic (AFM) and ferromagnetic (FM) phases at low temperatures. Electrical conductivity increased with temperature and reached a level of 4.3 S⋅cm−1in air at 1073 K, which indicates that the spinel exhibited semiconducting properties. This oxide can be considered as a material for protective-conducting coatings on ferritic stainless steel used to manufacture interconnects for solid oxide fuel cells.

Diamonds can be used as dosimeters due to their high sensitivity to the ionizing radiation, radiation hardness as well as mechanical and chemical resistance. Moreover diamond, as the allotropic form of carbon, is tissue-equivalent what is an important property in regard to its potential future application in medical physics. Diamond films deposited on Si substrates by chemical vapor deposition (CVD) method using SEKI plasma reactor at the Institute of Nuclear Physics in Krakow were investigated to the aspect of their thermoluminescent (TL) properties. The deposition was performed at different oxygen concentration and the thermoluminescence of diamond films was studied. All grown diamond films were characterized in terms of surface morphology (scanning electron microscopy), chemical (Raman spectroscopy) and structural properties (X-ray diffraction). The influence of three types of radiation: α (241Am, 5.49 MeV), β (90Sr/90Y, 2.27 MeV), γ (60Co, 1250 keV) on the shape of the TL curves was also examined.

The elemental and phase compositions and the magnetic state of metal particles in FeCoZr-Pb(ZrTi)O3 granular nanocomposites (GNCs) synthesized by ion-beam sputtering of composite targets in oxygen-containing media at different oxygen partial pressures have been studied. The phase transformations in GNCs have been monitored by the Raman and Mossbauer spectroscopy techniques. Correlation between the oxygen pressure during GNC synthesis and the valence state of iron ions in metal granules has been established. It has been confirmed that (i) the degree of metal oxidation increases with increasing oxygen pressure and (ii) the degree of crystallinity of oxides increases as a result of annealing. It has been established that the percolation threshold in GNCs can also be varied by changing the oxygen pressure during GNC synthesis.

International audience; Fe/Cr/Fe trilayers and Fe/Cr multilayers were irradiated by 163 MeV Au ions with fluence of 1 × 1011 ions/cm2 to 50 × 1011 ions/cm2. The structural properties of Fe/Cr interfaces were observed using Conversion Electron Mössbauer Spectroscopy (CEMS) and X-ray reflectivity (XRR). The magnetic exchange coupling between Fe layers through Cr spacer in trilayers and multilayers was determined from hysteresis loops measured with SQUID magnetometer. The different behavior of Fe/Cr/Fe trilayers and Fe/Cr multilayers was observed after Au ions irradiation. In Fe/Cr multilayers a decrease of the average value of hyperfine magnetic field with increasing Au ions fluence was observed, indicating an increase of the interfacial roughness. In Fe/Cr/Fe trilayers the non-monotonic behavior of average value of hyperfine magnetic field versus ion fluence was observed suggesting the smoothing of the interfaces at small fluences and roughening at higher ones. The smoothening of interfaces was confirmed by XRR spectra. In multilayers the magnetic properties changed in a similar way as the structural properties and continuous decay of antiferromagnetic coupling as a function of fluence was observed. In trilayers at the low fluences the antiferromagnetic coupling was not sensitive on irradiation, while at large fluences the decrease of antiferromagnetic coupling fraction was seen.