Coupling of spin and lattice modes in theS=1/2two-dimensional antiferromagnet K2V

Abstract

Lattice dynamics and magnetic excitations are investigated to elucidate the origin of magnetodielectric effects in the S=1/2 two-dimensional quantum spin compound K2V3O8. We find evidence for lattice instabilities at 110 K and 60 K as optical phonon anomalies and a soft mode at 26 cm −1 in A1 symmetry. Two-magnon excitations in B1 symmetry show an unconventional double-peak structure and temperature dependence. This suggests the existence of a split mode near the zone boundary caused by a mixing of spin and lattice modes.

High-pressure behaviour of Cs2V3O8 fresnoite

“…The phase transitions to the modulated structures are associated with anomalies in optical phonons and thermal properties. Magnetic properties of the vanadate fresnoites have been reported, among others, by Liu et al [9] and Choi et al [10]. These materials exhibit antiferromagnetic interactions at low temperatures and K 2 V 3 O 8 is considered to be a spin ½ quasi two-dimensional antiferromagnet [10].…”

V51 -NMR study on the S=12 square lattice antiferromagnet Takeda1, Yaśuoka2, Yoshida3 et al. 2019Phys. Rev. BSelf Cite

“…Infrared and Raman spectroscopy measurements revealed local lattice distortion in the V 4+ O 5 pyramid, [21][22][23] in particular, the stretching phonon mode for the V 4+ -O ap (apical oxygen) bond exhibits splitting at 115 K. Then it is likely that the V 4+ -O ap bond length has the same periodic modulation as the supertattice below T S as illustrated in Fig. 12(a) and (b).…”

“…Further experiments revealed a structural transition at T S ∼115 K. [21][22][23][24] While the splitting of of some phonon modes observed by infrared spectroscopy provides evidence for local distortion of VO 5 pyramids, [21][22][23] the magnetic susceptibility shows no anomaly at T S . 18,19 X-ray diffraction measurements detected weak superlattice reflections indicating a 3 × 3 × 2 supercell, whereas the precise structure has not been determined.…”

“…22 Raman spectroscopy also detected mixing between the spin wave excitations and phonon vibrations. 23 In this paper, we discuss microscopic structural and magnetic properties of K 2 V 3 O 8 based on 51 V NMR experiments on V 5+ sites. We observed splitting of the NMR lines below T S , which can be ascribed to the formation of superlattice and associated local distortion of the V 4+ O 5 pyramids.…”

In Situ and Operando Analyses of Reaction Mechanisms in Vanadium Oxides for Li‐, Na‐, Zn‐, and Mg‐Ions Batteries

“…This change of peak intensities is related to the deformation of the [VO 4 ] tetrahedron and the [VO 5 ] pyramids. [ 112,113 ] It is attributed from the extraction of K + in the first charge.…”