Abstract
Abstract
The pyrochlore iridates, A
2Ir2O7, show a wide variety of structural, electronic, and magnetic properties controlled by the interplay of different exchange interactions, which can be tuned by external pressure. In this work, we report pressure-induced iso-structural phase transitions at ambient temperature using synchrotron-based x-ray diffraction (up to ∼20 GPa) and Raman-scattering measurements (up to ∼25 GPa) of the pyrochlore series (Sm
_{1-x}
Bi
x
)2Ir2O7 (x = 0, 0.02, and 0.10). Our Raman and x-ray data suggest an iso-structural transition in Sm2Ir2O7 at
P
c
∼ 11.2 GPa, associated with the rearrangement of IrO6 octahedra in the pyrochlore lattice. The transition pressure decreases to ∼10.2 and 9 GPa for x = 0.02 and 0.10, respectively. For all the samples, the linewidth of three phonons associated with Ir–O–Ir (
A
1
g
and Eg
) and Ir–O (
T
2
g
4
) vibrations show anomalous decrease up to
P
c
, due to decrease in electron–phonon interaction.