1204.6210 (K. -Y. Choi et al.)

Coupling of spin and lattice modes in the S=1/2 two-dimensional
antiferromagnet K$_{2}$V$_{3}$O$_{8}$ with magneto-dielectric couplings    [PDF]

K. -Y. Choi, P. Lemmens, V. P. Gnezdilov, B. C. Sales, M. D. Lumsden

Lattice dynamics and magnetic excitations are investigated to elucidate the origin of magneto-dielectric effects in the S=1/2 two-dimensional quantum spin compound K$_2$V$_3$O$_8$. 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 A$_1$ symmetry. Two-magnon excitations in B$_1$ 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.

View original: http://arxiv.org/abs/1204.6210