  In Eu2ZnIrO6, effectively two atoms are active i.e. Ir is magnetically
active, which results in complex magnetic ordering within the Ir sublattice at
low temperature. On the other hand, although Eu is a van-vleck paramagnet, it
is active in the electronic channels involving 4f 6 crystal-field split levels.
Phonons, quanta of lattice vibration, involving vibration of atoms in the unit
cell, are intimately coupled with both magnetic and electronic degrees of
freedom (DoF). Here, we report a comprehensive study focusing on the phonons as
well as intra-configurational excitations in double-perovskite Eu2ZnIrO6. Our
studies reveal strong coupling of phonons with the underlying magnetic DoF
reflected in the renormalization of the phonon self-energy parameters well
above the spin-solid phase (TN ~ 12 K) till temperature as high as ~ 3TN,
evidences broken spin rotational symmetry deep into the paramagnetic phase. In
particular, all the observed first-order phonon modes show softening of varying
degree below ~3TN, and low-frequency phonons become sharper, while the
high-frequency phonons show broadening attributed to the additional available
magnetic damping channels. We also observed a large number of high-energy
modes, 39 in total, attributed to the electronic transitions between 4f-levels
of the rare-earth Eu3+ ion and these modes shows anomalous temperature
evolution as well as mixing of the crystal-field split levels attributed to the
strong coupling of electronic and lattice DoF.
