Raman spectroscopy ofCa3Ru2O7: Phonon line assignment and electron scattering

Abstract

The polarized Raman spectra of layered ruthenate Ca 3 Ru 2 O 7 were measured between 5 and 300 K in several exact scattering configurations. All observed Raman lines were assigned to definite phonon modes of A 1 or A 2 symmetry on the basis of their polarization properties and by comparison to the results of lattice dynamical calculations for the orthorhombic A2 1 ma structure. It is established that the Fano-shaped A 2 mode, which exhibits a strong anomaly near the metal-nonmetal transition at T M = 48 K, involves mainly in-plane breathingtype oxygen vibrations. Other A 2 modes also exhibit detectable anomalies near T M . We argue that the phonon softening below T M is largely due to the orbital ordering and related structural changes.

Hidden phases revealed at the surface of double-layeredSr3(Ru1−xMChen1, Kim2, Nascimento3 et al. 2016Phys. Rev. B91110View full textAdd to dashboardCite

“…This asymmetric line-shape is typical for a Fano process, resulting from the interference between a discrete resonance scattering process ( 3 ω ) and a continuum of background [42]. This Fano line-shape is seen in previous Raman spectroscopy study on Ca 3 Ru 2 O 7 [41,43,44]. In this case, the "resonance" is the phonon excitation, and the "continuum" is the electron-hole pairing excitations.…”

Spectroscopic study of the field- and pressure-induced phases of the bilayered ruthenateCa3Ru2O7

“…Figure 2 illustrates the Raman scattering spectrum of Ca 3 Ru 2 O 7 in its antiferromagnetic ͑T = 11.5 K, H = 0 T, and P = 0 kbar͒ and metallic ͑T =58 K, H = 0 T, and P = 0 kbar͒ phases for the frequency range 40-500 cm −1 . To explore the field-and pressure-induced spin and orbital configurations of Ca 3 Ru 2 O 7 , two key spectroscopic features will be examined in this paper: ͑i͒ a B 1g symmetry phonon mode near 416 cm −1 at 5 K, which is associated with out-of-phase vibrations of the RuO 6 octahedra; 16 and ͑ii͒ a low frequency mode near 56 cm −1 , which is associated with spin wave ͑magnon͒ excitations of the antiferromagnetic ground state.…”

“…This phonon mode is known to involve out-of-phase vibrations of the Ru-O octahedra ͓see Fig. 3͑b͔͒, 16 and consequently, the frequency of this mode is exquisitely sensitive to both the orbital population on the Ru ions and the dc conductivity. The latter is illustrated by comparing the temperature-dependent frequency of the B 1g mode to the dc conductivity in Fig.…”

Interplay of spin, lattice, vibration, and charge degrees of freedom: Magneto‐dielectricity in Ca3Mn2O7

“…The Raman Figure 5A over 5-300 K. The two most prominent phonon modes have been recognized as A 1 (15) and A1 (17) for the Cmc21 phase (=A21ma structure with 'c'-long axis). 21 Lorentzian peak-fit analysis ( Figure 5B,C) has been carried out for the respective modes, to obtain thermal evolution of the phonon modes. Peak characteristics follow the classical behavior;…”