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Register a new userSolution enthalpies of barium cerates co-doped by rare-earth elements and indium
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N.I. Matskevich
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The dissolution enthalpies of BaCe0.7Ho0.2In0.1O2.85 and BaCe0.7Sm0.2In0.1O2.85 were measured by method of solution calorimetry in 1M hydrochloric acid with adding 0.1 M KI. The obtained data were compared with earlier measured data on dissolution enthalpies of BaCe0.7Nd0.2In0.1O2.85, BaCe0.7Gd0.2In0.1O2.85. The dependence of dissolution enthalpies from lanthanide radius was constructed. As was shown the relationship is not linear.
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The ferromagnetic (FM) nature of Nd2Fe14B has been investigated with muon spin rotation and relaxation ({mu}^+SR) measurements on an aligned, sintered plate-shaped sample. A clear muon spin precession frequency (f_{FM}) corresponding to the static internal FM field at the muon site showed an order parameter-like temperature dependence and disappeared above around 582 K (~T_C). This indicated that the implanted muons are static in the Nd2Fe14B lattice even at temperatures above around 600 K. Using the predicted muon site and local spin densities predicted by DFT calculations, the ordered Nd moment (M_{Nd}) was estimated to be 3.31 {mu}_B at 5 K, when both M_{Fe} and M_{Nd} are parallel to the c-axis and M_{Fe} = 2.1 {mu}_B. Furthermore, M_R in R2Fe14B with R = Y, Ce, Pr, Sm, Gd, Tb, Dy, Ho, Er, and Tm was estimated from f_{mu} values reported in earlier {mu}+SR work, using the FM structure proposed by neutron scattering and the same muon site and local spin density as in Nd2Fe14B. Such estimations yielded M_R values consistent with those obtained by the other methods.
Optically addressable spins are actively investigated in quantum communication, processing and sensing. Optical and spin coherence lifetimes, which determine quantum operation fidelity and storage time, are often limited by spin-spin interactions, which can be decreased by polarizing spins in their lower energy state using large magnetic fields and/or mK range temperatures. Here, we show that optical pumping of a small fraction of ions with a fixed frequency laser, coupled with spin-spin interactions and spin diffusion, leads to substantial spin polarization in a paramagnetic rare earth doped crystal, $^{171}$Yb$^{3+}$:YSO. Indeed, up to more than 90 % spin polarizations have been achieved at 2 K and zero magnetic field. Using this spin polarization mechanism, we furthermore demonstrate an increase in optical coherence lifetime from 0.3 ms to 0.8 ms, due to a strong decrease in spin-spin interactions. This effect opens the way to new schemes for obtaining long optical and spin coherence lifetimes in various solid-state systems such as ensembles of rare earth ions or color centers in diamond, which is of interest for a broad range of quantum technologies.
The X-ray magnetic circular dichroism (XMCD) has been measured at the Co K edge in Co-hcp and R-Co compounds (R=La, Tb, Dy). The structure of the experimental XMCD spectra in the near-edge region has been observed to be highly sensitive to the magnetic environment of the absorbing site. Calculations of the XMCD have been carried out at the Co K edge in Co metal, LaCo$_5$ and TbCo$_5$ within the multiple-scattering framework including the spin-orbit coupling. In the three systems, the XMCD spectra in the near-edge region are well reproduced. The possibility to separate and quantitatively estimate the local effects from those due to the neighboring atoms in the XMCD cross section makes possible a more physical understanding of the spectra. The present results emphasize the major role played by the $d$ states of the Tb ions in the XMCD spectrum at the Co K edge in the TbCo$_5$ compound.
Inelastic neutron scattering was employed to study the crystal-field interaction in the strontium-doped rare-earth compounds R(x)Sr(1-x)CoO(3-z) (R=Pr, Nd, Ho, and Er). Particular emphasis is laid on the effect of oxygen deficiencies which naturally occur in the synthesis of these compounds. The observed energy spectra are found to be the result of a superposition of crystal fields with different nearest-neighbor oxygen coordination at the R sites. The experimental data are interpreted in terms of crystal-field parameters which behave in a consistent manner through the rare-earth series, thereby allowing a reliable extrapolation for rare-earth ions not considered in the present work.
Solid state synthesis and physical mechanisms of electrical conductivity variation in polycrystalline, strontium doped indium oxide In2O3:(SrO)x were investigated for materials with different doping levels at different temperatures (T=20-300 C) and ambient atmosphere content including humidity and low pressure. Gas sensing ability of these compounds as well as the sample resistance appeared to increase by 4 and 8 orders of the magnitude, respectively, with the doping level increase from zero up to x=10%. The conductance variation due to doping is explained by two mechanisms: acceptor-like electrical activity of Sr as a point defect and appearance of an additional phase of SrIn2O4. An unusual property of high level (x=10%) doped samples is a possibility of extraordinarily large and fast oxygen exchange with ambient atmosphere at not very high temperatures (100-200 C). This peculiarity is explained by friable structure of crystallite surface. Friable structure provides relatively fast transition of samples from high to low resistive state at the expense of high conductance of the near surface layer of the grains. Microscopic study of the electro-diffusion process at the surface of oxygen deficient samples allowed estimation of the diffusion coefficient of oxygen vacancies in the friable surface layer at room temperature as 3x10^(-13) cm^2/s, which is by one order of the magnitude smaller than that known for amorphous indium oxide films.
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