NMR Studies of¹⁷O in the Normal State of YBa₂Cu₃O_6+x

NMR studies of pseudogap and electronic inhomogeneity in Bi2Sr2CaCu2OCrocker1, Dioguardi2, apRoberts-Warren3 et al. 2011Phys. Rev. B

“…We find C aa = 51 kOe/µ B and C bb = 80 kOe/µ B , similar to previous measurements in YBa 2 Cu 3 O 7−δ . 31 For the cdirection, χ c is essentially temperature independent, and we do not have enough precision to measure C cc ; however spin-lattice-relaxation rate measurements discussed below suggest that C cc ∼ C aa , in agreement with previous reports in YBa 2 Cu 3 O 7−δ . 31 The approximate axial symmetry of the transferred hyperfine coupling arises from the O 2p-orbitals that hybridize with the nearest neighbor Cu 4s orbitals.…”

“…31 For the cdirection, χ c is essentially temperature independent, and we do not have enough precision to measure C cc ; however spin-lattice-relaxation rate measurements discussed below suggest that C cc ∼ C aa , in agreement with previous reports in YBa 2 Cu 3 O 7−δ . 31 The approximate axial symmetry of the transferred hyperfine coupling arises from the O 2p-orbitals that hybridize with the nearest neighbor Cu 4s orbitals. 36 The pseudogap is manifest in NMR as a peak in the Knight shift at a temperature T m followed by a breakdown of scaling below a temperature T * .…”

“…We estimate the ratios R 0 a /R 0 b = 0.329 and R 0 c /R 0 b = 0.373 as the squares of the hyperfine coupling ratios, since R α ∼ h 2 α ∼ C 2 αα , where C αα is the hyperfine coupling. 31,36 In this approximation, we assume a single component coupling model to isotropic Cu S = 1/2 spins. In the limit γH 0 /ν bb → ∞ the eigenstates of (1) indeed commute withÎ z and the relaxation matrices reduce to their conventional forms that depend only on a single time constant.…”

“…17,21,30 Aligned powder samples have well resolved spectra for the applied field along the alignment axis (usually the c-direction), but exhibit a random powder pattern for perpendicular fields. 31 Although there are ways to extract parameters of the EFG and T −1 1 tensors from these powder patterns, there are usually unavoidable baseline and orientation distribution corrections. 21,32 On the other hand, isotopically enriched Bi 2 Sr 2 CaCu 2 O 8+δ single crystals enable one to measure directly the full shift, quadrupolar and spin-lattice-relaxation rate tensors.…”

Dynamic correlated Cu(2) magnetic moments in superconductingYBa2(Cu0.96Ni0.04Hodges1, Bonville2, Forget3 et al. 2009Phys. Rev. B2030View full textAdd to dashboardCite

“…The observed hyperfine coupling is dominated by coupling to the spin polarisation of the two nearest in-plane Cu(2) 32,33 . The measurements evidence a field induced staggered polarisation of the Cu(2) moments around each Ni and provide a direct static signature of the magnetic correlations within the Cu(2)-O planes.…”