Cross-relaxation and phonon bottleneck effects on magnetization dynamics in LiYF4:Ho3+

Frequency and dc magnetic field dependences of dynamic susceptibility in diluted paramagnets LiYF$_4$:Ho$^{3+}$ have been measured at liquid helium temperatures in the ac and dc magnetic fields parallel to the symmetry axis of a tetragonal crystal lattice. Experimental data are analyzed in the framework of microscopic theory of relaxation rates in the manifold of 24 electron-nuclear sublevels of the lowest non-Kramers doublet and the first excited singlet in the Ho$^{3+}$ ground multiplet $^5I_8$ split by the crystal field of S$_4$ symmetry. The one-phonon transition probabilities were computed using electron-phonon coupling constants calculated in the framework of exchange charge model and were checked by optical piezospectroscopic measurements. The specific features observed in field dependences of the in- and out-of-phase susceptibilities (humps and dips, respectively) at the crossings (anti-crossings) of the electron-nuclear sublevels are well reproduced by simulations when the phonon bottleneck effect and the cross-spin relaxation are taken into account

In situ X-ray diffraction investigation of nitride coatings at high-temperature oxidation

Structural and phase researches of the multicomponent nanocrystalline coatings synthesized by plasma-assisted vacuum arc method at high-temperature influence by method of X-ray diffraction with the use of synchrotron radiation in situ have been carried out. The main features of these coatings are the superhardness (39 - 45 GPa) and nanocrystalline structure (5 - 20 nm). The analysis of results of structural and phase researches, physical and mechanical characteristics after oxidation of multicomponent nitride coatings at high-temperature heating in open air is presented

THE INFLUENCE OF THERMAL REDUCTION ON THE CHARACTERISTICS OF LIGHSCRIBED GRAPHENE OXIDE HUMIDITY SENSOR

Humidity sensing structures based on graphene oxide (GO) were thermally reduced to obtain GO films with different reduction degrees. Measurements of conductivity of the reduced films were made under the change of relative humidity. Different types of humidity sensing characteristics were obtained and described.Работа проведена при поддержке гранта РФФИ №15-08-01977

Self-amplified spontaneous emission saturation at the Advanced Photon Source free-electron laser (abstract) (invited)

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In situ X-ray diffraction investigation of nitride coatings at high-temperature oxidation

Structural and phase researches of the multicomponent nanocrystalline coatings synthesized by plasma-assisted vacuum arc method at high-temperature influence by method of X-ray diffraction with the use of synchrotron radiation in situ have been carried out. The main features of these coatings are the superhardness (39 - 45 GPa) and nanocrystalline structure (5 - 20 nm). The analysis of results of structural and phase researches, physical and mechanical characteristics after oxidation of multicomponent nitride coatings at high-temperature heating in open air is presented

In situ X-ray diffraction studies of Pr2 − xNiO4 + δ crystal structure relaxation caused by oxygen loss

Fine powders of Pr2 − xNiO4 + δ (PNO) oxides (x=0÷0.3) synthesized by Pechini routewere uniaxially pressedinto pellets and sintered at 1300 °C under air. Chemical diffusion coefficients (Dchem.) and surface exchange constants(kchem.) were estimated by analysis of the weight and conductivity relaxations after step-wise change ofpO2. In situ XRD studies were carried out in VEPP-3 facilities of the Siberian Center of Synchrotron Radiationusing unique high-temperature camera and procedures.Analysis of dynamics of the cell volume expansion caused by oxygen loss with due regard for penetration depthof X-rays into the pellet allowed to estimate Dchem and kchem found to be close to those obtained by traditionalmethods. Isolated Pr vacancies appear to be the most important for fast oxygen diffusion and high surface reactivityproviding the highest values of kchem and Dchem for Pr1.9NiO4 + δ composition