Static and Resonant Properties and Magnetic Phase Diagram of LiMn2TeO6.

Physical properties of the mixed-valent tellurate of lithium and manganese, LiMn2TeO6, were investigated in measurements of ac and dc magnetic susceptibility χ, magnetization M, specific heat Cp, electron spin resonance (ESR), and nuclear magnetic resonance (NMR) in the temperature range 2−300 K under magnetic field up to 9 T. The title compound orders magnetically in two steps at T1 = 20 K and T2 = 13 K. The intermediate phase at T2 < T < T1 is fully suppressed by magnetic field µ0H of about 4 T. Besides magnetic phases transitions firmly established in static measurements, relaxation-type phenomena were observed well above magnetic ordering temperature in resonant measurements.

Hybrid Molecules Based on Fullerene C60 and Dithienylethenes. Synthesis and Photochromic Properties. Optically Controlled Organic Field-Effect Transistors.

Hybrid molecules based on fullerene C60 and dithienylethene and its perfluorinated analog not inferior in the efficiency of phototransformations to the initial photochromic compounds were synthesized for the first time. The resulting pyrrolidinofullerenes containing photochromic moieties were used to fabricate organic field-effect transistors (OFETs) with output and transfer characteristics ten times exceeding similar characteristics of devices based on staring dithienylethenes. It was found that OFETs based on hybrid molecules with dithienylethenes are four times less efficient than devices based on hybrid molecules with perfluorinated analogs.

Photoconductivity of Thin Films Obtained from a New Type of Polyindole.

The optoelectronic properties of a new poly(2-ethyl-3-methylindole) (MPIn) are discussed in this paper. The absorption and photoluminescence spectra were studied. The electronic spectrum of MPIn showed a single absorption maximum at 269 nm that is characteristic of the entire series of polyindoles. The fluorescence spectra show that the emission peaks of the test sample are centered around 520 nm. The photoconductivity of thin film samples of MPIn polyindole was studied by measuring the current-voltage characteristics under ultraviolet radiation with a wavelength of 350 nm. Samples of phototransistors were obtained, where thin films of MPIn polyindole were used as a transport layer, and their characteristics were measured and analyzed. The value of the quantum efficiency and the values of the mobility of charge carriers in thin polyindole films were estimated.

Effects of Non-Stoichiometry on the Ground State of the Frustrated System Li0.8Ni0.6Sb0.4O2.

The non-stoichiometric system Li0.8Ni0.6Sb0.4O2 is a Li-deficient derivative of the zigzag honeycomb antiferromagnet Li3Ni2SbO6. Structural and magnetic properties of Li0.8Ni0.6Sb0.4O2 were studied by means of X-ray diffraction, magnetic susceptibility, specific heat, and nuclear magnetic resonance measurements. Powder X-ray diffraction data shows the formation of a new phase, which is Sb-enriched and Li-deficient with respect to the structurally honeycomb-ordered Li3Ni2SbO6. This structural modification manifests in a drastic change of the magnetic properties in comparison to the stoichiometric partner. Bulk static (dc) magnetic susceptibility measurements show an overall antiferromagnetic interaction (Θ = -4 K) between Ni2+ spins (S = 1), while dynamic (ac) susceptibility reveals a transition into a spin glass state at a freezing temperature TSG ~ 8 K. These results were supported by the absence of the λ-anomaly in the specific heat Cp(T) down to 2 K. Moreover, combination of the bulk static susceptibility, heat capacity and 7Li NMR studies indicates a complicated temperature transformation of the magnetic system. We observe a development of a cluster spin glass, where the Ising-like Ni2+ magnetic moments demonstrate a 2D correlated slow short-range dynamics already at 12 K, whereas the formation of 3D short range static ordered clusters occurs far below the spin-glass freezing temperature at T ~ 4 K as it can be seen from the 7Li NMR spectrum.