Raman scattering from magnetic excitations in the spin-ladder compoundsCaV2O5and

M.J. Konstantinović

¹

,

Zdenka Popović

²

,

Masahiko Isobe

³

et al.

Abstract

We present the Raman-scattering spectra of CaV 2 O 5 and MgV 2 O 5 . The magnetic contribution in the Raman spectra of CaV 2 O 5 is found in the form of a strong asymmetric line, centered at 2∆ S , with a tail on the high-energy side. Our analysis of its spectral shape shows that the magnetic ordering in CaV 2 O 5 can be described using a S=1/2 two-leg ladder Heisenberg antiferromagnetic model with J /J ⊥ ∼ 0.1, and a small interladder exchange. The spin gap and exchange constant are estimated to be ∆ s ∼ 400 cm −1 (570 K) and J ⊥ ∼ 640 K. No magnon bound states are found. In contrast to CaV 2 O 5 the existence of the spin-gap is not confirmed in MgV 2 O 5 , since we found no feature in the spectra which could be associated with the onset of the twomagnon continuum. Instead, we observe two-magnon excitation at 340 cm −1 , presumably related to the top of the two-magnon brunch.

Optical properties, electron-phonon coupling, and Raman scattering of vanadium ladder compounds

“…the in-phase motion of Ca with the other atoms of the ladder (chain rotation) has higher energy than the out-of-phase vibration, where Ca vibrates c in opposite direction to the ladder. 45) which has been assigned as an A g mode in both papers. In the latter case our calculated frequency of 265 cm −1 can be related to the measured 282 cm −1 vibration.…”

Raman response in antiferromagnetic two-leg S = 1/2 Heisenberg ladders

“…3 the Raman shift for CaV 2 O 5 [8] is shown. This substance is a quasi-2D layered material where the S = 1/2 V 4+ ions form weakly coupled 2-leg ladders (trellis lattice).…”

“…There are several experimental realizations of spin ladders like CaV 2 O 5 , SrCu 2 O 3 and La y Ca 14−y Cu 24 O 41 rendering direct comparison between theory and experiment possible [7][8][9][10][11].…”

Magnetodielectric effect in theS=1∕2quasi-two-dimensional antiferromagnetK2V3Rai1, Cao2, Musfeldt3 et al. 2006Phys. Rev. B250380View full textAdd to dashboardCite

“…Several modes show softening and splitting at low temperature, evidence of the 110 K structural distortion and a soft lattice. Based on vibrational properties studies in similar vanadyl oxide compounds, 67,68,69,70,71 the features of interest below 500 cm −1 can be assigned as V-O-V bending, O-V-O bending, and other low-energy tortional and twisting motions of the square pyramidal and tetrahedral building block units. The behavior of the 6.8 meV (55 cm −1 ) cluster (Fig.…”