Temperature-dependent Raman and x-ray studies of the spin-ice pyrochlore Dy2Ti2O7 and nonmagnetic pyrochlore Lu2Ti2O7

Article

关键词: RARE-EARTH TITANATES;    GEOMETRICAL FRUSTRATION;    OPTICAL PHONONS;    HO2TI2O7;    SPECTRA;    FERROMAGNET;    SCATTERING;    PRESSURE;    SYSTEM;    PHASE;   

DOI  :  10.1103/PhysRevB.78.214102

来源: SCIE

【 摘 要 】

We present here temperature-dependent Raman, x-ray diffraction, and specific heat studies between room temperature and 12 K on single crystals of spin-ice pyrochlore compound Dy2Ti2O7 and its nonmagnetic analog Lu2Ti2O7. Raman data show a new band not predicted by factor group analysis of Raman-active modes for the pyrochlore structure in Dy2Ti2O7, appearing below a temperature of T-c=110 K with a concomitant contraction of the cubic unit cell volume as determined from the powder x-ray diffraction analysis. Low-temperature Raman experiments on O-18-isotope substituted Dy2Ti2O7 confirm the phonon origin of the new mode. These findings, absent in Lu2Ti2O7, suggest that the room-temperature cubic lattice of the pyrochlore Dy2Ti2O7 undergoes a subtle structural transformation near T-c. We find anomalous redshift of some of the phonon modes in both the Dy2Ti2O7 and the Lu2Ti2O7 as the temperature decreases, which is attributed to strong phonon-phonon anharmonic interactions.

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