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'N Q R' in keywords
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1994 (4)
1986 (1)
1Author    Z. NaturforschRequires cookie*
 Title    An ESR Study of Structural Phase Transitions o f(N H ,)2Pb|C u(N 02)6|  
 Abstract    T etsuo Asaji, Laxm an S hrikrishna P ra b h u m irash i *, and D aiy u N ak a m u ra The structural changes o f (N H 4) 2P b [C u (N 0 2)6] crystals during the phase transitions at 316, 287, and 95 K were studied by means o f a single crystal ESR technique. Anisotropic g values [9 > 9±) were obtained in the lowest temperature phase IV, whereas the ESR spectra recorded in the intermediate phases III and II, in which the crystal is known to be tetragonally compressed along the c axis, could be interpreted by use o f effective g values [g (c) < g (_L c)]. In the highest temperature phase I an isotropic g value was obtained. The phases I, II, and III o f the present complex can be assumed to be very similar to the corresponding phases observed above ~ 250 K for the com pounds R2P b [C u (N 0 2) 6] with R = K, Rb, Cs, and Tl. However, the lowest temperature phase transition transforms the phase III with an antiferrodistortive order o f the elongated [C u (N 0 2)6]4_ octahedra into the phase IV with a ferrodistortive one. This occurs only for the complex with R = N H 4 and is very unusual. The results o f the 14N N Q R experiments already reported for the phases III and IV could be well explained by the present newly proposed model. 
  Reference    Z. Naturforsch. 41a, 1154—1158 (1986); received May 3 1986 
  Published    1986 
  Keywords    Magnetic Resonance (ESR, N Q R ), Phase Transition, Crystal Structure 
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 TEI-XML for    default:Reihe_A/41/ZNA-1986-41a-1154.pdf 
 Identifier    ZNA-1986-41a-1154 
 Volume    41 
2Author    N. F. Peirson, J.A S Smith, D. StephensonRequires cookie*
 Title    70 Quadrupole Dips in Ammonium Persulphate  
 Abstract    The magnetic field dependence of the *H spin-lattice relaxation time in ammonium persulphate shows pronounced minima near the JH magnetic resonance frequencies of 1,200 and 2,200 kHz. These are interpreted in terms of a m odel involving cross-relaxation between *H in the N H 4 ion and 170 in natural abundance in the S2O g_ ions, the latter having a much shorter spin-lattice relaxation time. A theoretical analysis of the shape of the minima is used to derive values for the 170 quadrupole parameters. This analysis results in best estimate values for the quadrupole coupling constant of 6.75 (± 0.05) M Hz and an asymmetry of 0.30 (± 0.02). Such values are indicative o f O -H hydrogen bonding and suggest the S2O g _ ion is not undergoing rapid reorientation at temperatures below 320 K. 
  Reference    Z. Naturforsch. 49a, 345 (1994); received August 16 1993 
  Published    1994 
  Keywords    N M R, N Q R, Field cycling, Oxygen-17 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0345.pdf 
 Identifier    ZNA-1994-49a-0345 
 Volume    49 
3Author    M. V. Eremin, R. Markendorf, S. G. SolovjanovRequires cookie*
 Abstract    The energy dispersion of the chain band has been determined in the framework of the Hubbard model. The results are in agreement along the T-S and T -Y lines of the Brillouin zone with photoemission data. The amount of d 3z2_r2 states is zero at y = 0 and increases to 10% at y = 1. The admixture is due to the hybridization of C u (l) dy2_z2 states with Cu(2) d 322_P2 states via apical oxygen. The effect of this admixture on the N Q R frequency of Cu(2) is discussed. 
  Reference    Z. Naturforsch. 49a, 379—384 (1994); received September 7 1993 
  Published    1994 
  Keywords    N Q R, Electron correlation, Chain band, d 3z2_r2 states, Band dispersion 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0379.pdf 
 Identifier    ZNA-1994-49a-0379 
 Volume    49 
4Author    M. V. EreminRequires cookie*
 Title    Why is the Cu(2) Asymmetry Parameter of N Q R Spectra in HTSC so Small?  
 Abstract    An explanation has been proposed for the unusual behaviour of the asymmetry parameter of N Q R spectra of Cu(2) in layered cuprates. When holes are introduced into the plane, Zhang-Rice singlets (ZRS) appear which have a strong vibronic coupling to tetragonal and orthorhombic modes. The equation for the adiabatic potential has been derived. It is shown that its minimum, correspond­ ing to orthorhombic distortions of the oxygen plaquette around the Cu(2) ions, changes under doping to tetragonal character due to the singlet exchange coupling between copper and oxygen holes. A strong interaction of ZRS via the phonon field has been found. 
  Reference    Z. Naturforsch. 49a, 385—388 (1994); received August 17 1993 
  Published    1994 
  Keywords    N Q R, Singlet correlation, Adiabatic potential, Tetragonal mode, Phonon coupling 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0385.pdf 
 Identifier    ZNA-1994-49a-0385 
 Volume    49 
5Author    Y. Kume, T. A. Sajia, R. IkedaRequires cookie*
 Title    Low Temperature Isotope Effect in Ammonium Hexachloroselenate(IV) Studied by 35C1 NQR  
 Abstract    The temperature dependence o f the 35C1 N Q R frequency and spin-lattice relaxation time TlQ of (N H 4)2SeCl6 and (N D 4)2SeCl6 were measured from 400 K to 24.8 and 53.8 K, respectively. The disappearance of N Q R signals in the low temperature region of both salts is attributed to phase transitions. We concluded from the temperature behavior of just above the transition point that the operative mechanism o f the transition is different in these salts: The transition of (N D 4)2SeCl6 seems to be associated with rotary soft modes, while in the natural salt non-rotary soft modes seem to play an important role at the transition. 
  Reference    Z. Naturforsch. 49a, 297 (1994); received August 13 1993 
  Published    1994 
  Keywords    Isotope effect, Spin-lattice relaxation, N Q R, Phase transition, Ammonium hexa­ chloroselenate, Deuterated am m onium hexachloroselenate 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0297.pdf 
 Identifier    ZNA-1994-49a-0297 
 Volume    49