Spin dynamics inSr14Cu24O41

Two-magnon Raman scattering in spin-ladder geometries and the ratio of rung and leg exchange constants

“…On the other hand, some local density approximation calculations 18,19 find the ratio to be closer to 0.5. A number of other studies which allow the ratio to vary, also find values close to ∼ 0.5 16,17,15 , although a range of experimental values from 0.5 to 1.13 have been quoted 15,[20][21][22][23] . Brehmer et al 24 make an interesting attempt to reconcile the conflicting viewpoints, keeping the ratio to be unity but allowing an additional biquadratic ring-interaction in the Hamiltonian.…”

Hole redistribution inSr14−xCaxCu24O41Piskunov1, Jérôme2, Auban‐Senzier3 et al. 2005Phys. Rev. B398291View full textAdd to dashboardCite

“…Such an increase of Q was reported in several NMR studies of Sr 2 Ca 12 Cu 24 O 41 . [21][22][23] In those works, it was indicated that the variation of Q is negligible in the low T regime but becomes quite appreciable above T Ϸ 100 K. Therefore, K c ͑T͒ vs. K b ͑T͒ plots were fitted by straight lines in the temperature range below 100 K. As a result of the fit, A b ͑0͒ / A c ͑0͒ = 2.6± 0.1 is independent of the applied pressure. This finding agrees well with A b ͑0͒ / A c ͑0͒ = 2.5 derived in Ref.…”

17Oand63CuNMR in Undoped and Hole Doped

“…By fitting NMR properties to the activation law,~exp͑2D͞k B T ͒, they tried to gain insight into the spin gap. Unfortunately, the coexistence of various charge and magnetic orders below 300 K makes even the estimation of the magnitude of the minimum of the gap D difficult, resulting in contradictory reports [6][7][8][9][10][11].In this Letter, we report the first 17 O NMR as well as 63 Cu NMR in the undoped and hole-doped Cu 2 O 3 plane of A 14 Cu 24 O 41 not only in the gapped low temperature regime but also in the high temperature paramagnetic regime, and demonstrate the crossover between the two. The comparison of 17 O and 63 Cu NMR results provides wave-vector-dependent experimental information regarding the evolution of spin excitations as functions of both temperature and hole doping.…”

“…By fitting NMR properties to the activation law,~exp͑2D͞k B T ͒, they tried to gain insight into the spin gap. Unfortunately, the coexistence of various charge and magnetic orders below 300 K makes even the estimation of the magnitude of the minimum of the gap D difficult, resulting in contradictory reports [6][7][8][9][10][11].…”

“…In the past few years, several groups reported 63 Cu NMR measurements in the Cu 2 O 3 ladder of SrCu 2 O 3 [6] and A 14 Cu 24 O 41 [7][8][9][10][11]. Since the spin gap D in these systems is as large as *300 K, these earlier experiments probed mostly the physical properties in the low temperature limit.…”