Raman scattering study of phonons in KCuF3

Phononic and magnetic excitations in the quasi-one-dimensional Heisenberg antiferromagnet KCuF3

“…At room temperature all lines have a Lorentzian lineshape. The observed spectra and mode assignments are in agreement with previously reported data at 10 K [18]. A direct comparison of our data at 4 K and 290 K with Ref.…”

“…The number of lines and the selection rules are fully consistent with the theoretically expected Raman-active normal modes [18] …”

“…In contrast, the E g (2) mode shows a splitting only when measuring in xz configuration. The E g (3) mode, which corresponds to a vibration of K + ions, shows no splitting in either of the two configurations [18]. The E g (1) and E g (2) modes correspond to shearing vibrations of the -F ions which involve a displacement of the fluorine ions away from the Cu-F-Cu bonding lines, while the B 1g mode corresponds to a tilting motion of the F -ions around the central Cu atom.…”

“…A direct comparison of our data at 4 K and 290 K with Ref. 18 and theoretical estimates [28] In the following we will focus on the temperature dependence of the phonon modes in KCuF 3 and mostly E g (1), E g (2) and B 1g . In Figs.…”

“…Nevertheless, the established symmetry assignment of the 18 4h D phase has been questioned by an x-ray diffraction investigation [17] which suggests the existence of orthorhombic distortions in KCuF 3 at room temperature with 4 2 D symmetry. A low-temperature Raman scattering (RS) study [18] reveals a difference of spectra measured in xz and yz polarization and anomalously broad linewidths of the stretching modes, which are interpreted as evidence of symmetry lower than 18 4h D also below the Néel temperature. Although orthorhombic distortions are involved for explaining the electron spin resonance (ESR) properties of KCuF 3 [19], discrepancies remain for the analysis of recent NQR [20], AFM resonance [21], and further experimental and theoretical findings [22,23].…”