Determination of the dislocation structure in paratellurite single crystals using the piezo-optic effect

It is shown theoretically and experimentally that dislocations in paratellurite single crystals can be revealed using the piezo-optic effect. The mechanical-stress distribution near dislocations is calculated. Dislocations in the samples are observed using the photoelastic method and chemical etching. Data on the spatial distribution of dislocations in Czochralski-grown paratellurite crystals are reported.     

Spirocyclic derivatives of nitronyl nitroxides in the design of heterospin CuII complexes manifesting spin transitions

A method was developed for the synthesis of a nitronyl nitroxide containing cyclopentane substituents in positions 4 and 5 of the imidazoline ring, viz., 2-(3-pyridyl)-4,5-bis(spiropentyl)-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (L^CP). The reaction of Cu^II hexafluoroacetylacetonate with L^CP affords different products depending on the reaction conditions: mononuclear [Cu(hfac)₂(L^CP)₂], binuclear [Cu(hfac)₂L^CP]₂, tetranuclear {[Cu(hfac)₂]₄(L^CP)₂}, or chain polymer {[Cu(hfac)₂]₃(L^CP)₂} _n . Temperature changes induce structural transformations accompanied by a change in the spin state in exchange clusters in the solid [Cu(hfac)₂L^CP]₂ and {[Cu(hfac)₂]₄(L^CP)₂}.     

Backward-wave regime and negative refraction in chiral composites

Possibilities to realize a negative refraction in chiral composites in dual-phase mixtures of chiral and dipole particles are studied. It is shown that because of a strong resonant interaction between chiral particles (helices) and dipoles, there is a stop band in the frequency area where the backward-wave regime is expected. The negative refraction can occur near the resonant frequency of chiral particles. Resonant chiral composites may offer a root to realization of negative-refraction effect and superlenses in the optical region.