Observation of quasi-elastic light scattering in BiFeO₃

Abstract

We observed quasi-elastic light scattering (QELS) in BiFeO3 using Raman spectroscopy over a temperature range of 300-860 K. The QELS has two components: a narrow and broad component. The temperature dependence of the intensity and linewidth of the broad component differed below and beyond the Néel point, and the broad QELS may have a magnetic origin.

Chiral phonons: circularly polarized Raman spectroscopy and ab initio calculations in a chiral crystal tellurium

“…The frequency differences between the RL and LR peaks of Samples 1 and 2 and those in Pine and Dresselhaus 35 are listed in Table 2. Such splitting has also been observed in Raman spectroscopy in ‐quartz, 50,51 Te, 35 and ‐HgS 11 …”

Brillouin scattering of multiferroic BiFeO3

“…12,41,42) In the future, we would like to perform polarization angleresolved measurements to investigate the relation with the cycloidal structure of spins. In addition, it has been reported in Raman scattering experiments that the magnon behavior changes between right and left circularly polarized light, 26) and we believe that circularly polarized Brillouin spectroscopy may clarify the cause of the anomalous TA2 behavior. The laser spot size in this experiment was 100 μm, while the antiferromagnetic domain of the sample used in this study was measured to be only a few μm.…”

“…[14][15][16][17][18][19] Among them, there are many reports on Raman scattering occurring in the relatively HF region, namely, above ∼10 cm −1 or 0.3 THz, where the optical phonons and magnons associated with the dielectric and magnetic ordering have been observed. [20][21][22][23][24][25][26] However, there are few reports on Brillouin scattering in the sub-100 GHz frequency region, where the acoustic phonons and magnons are expected to be observed. The acoustic phonons in BFO have been observed by using pump-probe spectroscopy 27,28) and pulse echo spectroscopy 29) in polycrystalline samples, but there is no direct observation of the Brillouin light scattering in single crystals of BFO to the best of our knowledge.…”

Angular‐Momentum Transfer Mediated by a Vibronic‐Bound‐State

“…Similar results have been reported for E symmetry Raman modes in TMDs, CrBr 3 , and quartz, among other materials. [9,60,61] Finally, moving on to the VBS 𝜔, it is much stronger in the cocircular polarization configuration and its magnetic field dependence is weak (Figures 2 and 3), in stark contrast to CEF1-3. This indicates that the change in angular momentum for 𝜔 is zero: ΔJ z = 0.…”

“…In other words, the angular momentum conservation rule is relaxed so that the total change of angular momentum can be either zero or a multiple of 3ℏ due to the threefold rotational symmetry. [59][60][61] This means that in the (𝜎 + , 𝜎 − ) configuration where ΔJ photon = −2ℏ, ΔJ system can be +2ℏ or −ℏ to satisfy the relaxed angular momentum conservation rule. For ΔJ system = +2ℏ, it corresponds to the operation of J + J + , while for ΔJ system = −ℏ, it corresponds to J − .…”