Temperature dependent Raman and x-ray studies of spin-ice pyrochlore $D{y}_{2}T{i}_2{O}_7$ and non-magnetic pyrochlore $L{u}_{2}T{i}_2{O}_7$

Abstract

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 $D{y}_{2}T{i}_2{O}_7$ and its non-magnetic analogue $L{u}_{2}T{i}_2{O}_7$. Raman data show a "new" band not predicted by factor group analysis of Raman-active modes for the pyrochlore structure in $D{y}_{2}T{i}_2{O}_7$, 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 $D{y}_{2}T{i}_2{O}_7$ confirm the phonon origin of the "new" mode. These findings, absent in $L{u}_{2}T{i}_2{O}_7$, suggest that the room temperature cubic lattice of the pyrochlore $D{y}_{2}T{i}_2{O}_7$ undergoes a "subtle" structural transformation near $T_c$. We find anomalous \textit{red-shift} of some of the phonon modes in both the $D{y}_{2}T{i}_2{O}_7$ and the $L{u}_{2}T{i}_2{O}_7$ as the temperature decreases, which is attributed to strong phonon-phonon anharmonic interactions.

28 pages, 9 figures (Accepted for publication in Physical Review B)

References in corpus (4)

• Phonon and crystal field excitations in geometrically frustrated rare earth titanates
• Manifestation of geometric frustration on magnetic and thermodynamic properties of pyrochlores $S{m}_2{X}_2{O}_7$ (X=Ti, Zr)
• High-temperature spin relaxation process in Dy${}_2$Ti${}_2$O${}_7$ probed by ${}^{47}$Ti-NQR
• Ordered spin-ice state in the geometrically frustrated metallic-ferromagnet Sm2Mo2O7

Cited by in corpus (1)

• Low temperature and high pressure Raman and x-ray studies of pyrochlore Tb${}_2$Ti${}_2$O${}_7$ : phonon anomalies and possible phase transition