Structural, hyperfine, and magnetic properties ofR2FeTaO7compounds (R=Y, Dy, Gd, and Eu)

Exciton Lifetime Paradoxically Enhanced by Dissipation and Decoherence: Toward Efficient Energy Conversion of a Solar Cell

“…Moreover, our results are consistent with the experimental indications [21][22][23][24]. In the SWCNT, at least two dark exciton states exist with energy below the lowest bright one [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]: Even-parity dark exciton [22,32,33] and spintriplet dark exciton [24,34,35]. The weak couplings between the bright and the dark excitons can strongly affect the exciton dynamics after the photon absorption.…”

“…Since κ strongly depends on the ambient solvents, matrices, and/or substrates, we vary κ over several orders of magnitude with keeping κ as a small parameter. The energy levels of bright and dark excitons are estimated from the photoluminescence experiments [21,[32][33][34][35]. The cutoff frequency of the spectral density ω cut is determined from the density of states of phonons in SWCNTs [39].…”

Synthesis, X-ray Rietveld analysis, infrared and Mössbauer spectroscopy of R 2 FeSbO 7 (R 3+ = Y, Dy, Gd, Bi) pyrochlore solid solution

“…No clear magnetic phase transition to a long-range ordered phase down to 2 K was observed in the magnetic measurement of R 2 FeTaO 7, in spite of the hyperfine magnetic field revealed by MS sextet splitting at 5 K [36]. Thus the well-defined sextet was attributed to the small islands of magnetically oriented Fe ions due to Fe-O-Ta-O-Fe superexchange coupling in R 2 FeTaO 7 [36].…”

“…No clear magnetic phase transition to a long-range ordered phase down to 2 K was observed in the magnetic measurement of R 2 FeTaO 7, in spite of the hyperfine magnetic field revealed by MS sextet splitting at 5 K [36]. Thus the well-defined sextet was attributed to the small islands of magnetically oriented Fe ions due to Fe-O-Ta-O-Fe superexchange coupling in R 2 FeTaO 7 [36]. On the other hand, in a recent magnetic measurement (unpublished) of Y 2 FeSbO 7 and Dy 2 FeSbO 7 polycrystals, a weak divergence in the field-cooled and zero-field-cooled susceptibilities is observed at ~9-10 K for both these samples, which may be considered as an onset of magnetic transition at this temperature.…”

“…splitting in the MS of R 2 FeSbO 7 [6,10,11,33,35,36], Y 2 Fe 1.33 W 0.67 [37], and also in the 5 K spectra of R 2 FeTaO 7 compounds [36]. No clear magnetic phase transition to a long-range ordered phase down to 2 K was observed in the magnetic measurement of R 2 FeTaO 7, in spite of the hyperfine magnetic field revealed by MS sextet splitting at 5 K [36].…”