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1992 (1)
1990 (1)
1Author    W. W. Warren, R. E. WalstedtRequires cookie*
 Title    NQR and NMR Studies of Spin Dynamics in High T c Superconducting Cuprates  
 Abstract    Recent NQR and NMR studies of Cu spin dynamics in metallic YBa 2 Cu 3 0 6+JC are reviewed. The Cu nuclear relaxation rates are shown to be inconsistent with weak correlation (band) theory and the Korringa relation, but the Cu spins retain important characteristics of itinerancy. These include pairing of the Cu d-spins in the superconducting state and strong sensitivity of the Cu spin dynamics to changes in carrier concentration associated with variation of the oxygen content. Samples of reduced oxygen content (T c = 60 K) are found to contain a high concentration of Cu + Cu(l) sites associated with "full chain-empty chain" vacancy ordering. These samples also exhibit remarkable precursive suppression of planar Cu(2) nuclear relaxation above T c . 
  Reference    Z. Naturforsch. 45a, 385—392 (1990); received October 25 1989 
  Published    1990 
  Keywords    NMR, NQR, Nuclear relaxation, Spin fluctuations, Superconductivity 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0385.pdf 
 Identifier    ZNA-1990-45a-0385 
 Volume    45 
2Author    Keizo Horiuchi, Daiyu NakamuraRequires cookie*
 Title    Chlorine Nuclear Spin-Spin Relaxation Mechanism in Mg(H 2 0) 6 SnCl 6 as Studied by NQR and NMR Techniques  
 Abstract    The 35 C1 NQR spin-lattice relaxation time T1Q, spin-spin-relaxation time T2Q, and J H NMR spin-lattice relaxation time in the rotating frame T le in Mg(H20)6SnCl6 were measured as functions of temperature. Above room temperature T2q increased rapidly with increasing temperature, which can be explained by fluctuations of the local magnetic field at the chlorine nuclei due to cationic motions. From the T le experiments, these motions are found to be attributable to uniaxial and overall reorientations of [Mg(H20)6] 2+ ions with activation energies of 95 and 116 kJ mol -1 , respectively. Above ca. 350 K, T1Q decreased rapidly with increasing temperature, which indicates a reorientational motion of [SnCl6] 2-ions with an activation energy of 115 kJ mol -1 . 
  Reference    Z. Naturforsch. 47a, 277—282 (1992); received October 29 1991 
  Published    1992 
  Keywords    Complex compounds, Molecular dynamics, Nuclear relaxation, Nuclear quadrupole resonance, Nuclear magnetic resonance 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0277.pdf 
 Identifier    ZNA-1992-47a-0277 
 Volume    47