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1Author    R. BlincRequires cookie*
 Title    NQR in Dipolar and Quadrupolar Glasses  
 Abstract    It is shown that nuclear quadrupole resonance and quadrupole perturbed magnetic resonance represent a powerful technique to determine the local polarization distribution and its second moment, the Edwards-Anderson order parameter, in proton and deuteron glasses. For quadrupolar glasses the local orientational distribution function can be determined from the inhomogeneous NMR or NQR lineshape, thus allowing for a measurement of the quadrupolar Edwards-Anderson order parameter. The comparison of the temperature dependences of the thus obtained order parameters with theoretical predictions then allows for a discrimination between the different possible models of the glassy transition. 
  Reference    Z. Naturforsch. 45a, 313—322 (1990); received August 22 1989 
  Published    1990 
  Keywords    NQR, Glasses, Order parameters 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0313.pdf 
 Identifier    ZNA-1990-45a-0313 
 Volume    45 
2Author    Mariusz Máckowiak, Costas DimitropoulosRequires cookie*
 Title    Calculation of NQR v's and T l s being proportional to T 4 and T 5 , respectively  
 Abstract    The second-order Raman phonon process for a multilevel spin system is shown to give a quadru-polar spin-lattice relaxation rate T x ~ varying as T 5 at very low temperatures. This relaxation rate for quadrupole spins is similar to the one discussed for a paramagnetic spin system having a multilevel ground state. The temperature dependence of Tj is discussed on the basis of some simplifying assumptions about the nature of the lattice vibrations in the Debye approximation. This type of relaxation process has been observed below 20 K in tetramethylammonium hydrogen bis-trichloroacetate for the 35 C1 Ti _1 . Below 20 K the NQR frequency in the same crystal reveals a T 4 temperature dependence due to the induced modulations of the vibrational and librational coordinates by the low-frequency acoustic phonons. 
  Reference    Z. Naturforsch. 45a, 536—540 (1990); received August 22 1989 in revised form November 24 1989 
  Published    1990 
  Keywords    Quadrupole relaxation, low temperature, NQR 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0536.pdf 
 Identifier    ZNA-1990-45a-0536 
 Volume    45 
3Author    Theresa Varty, R. Julian, C. Brown, FrancisP. TemmeRequires cookie*
 Title    Optimal Zeeman-NQR Powder Lineshape Calculations for 3/2^/^7/2  
 Abstract    The powder lineshapes, associated with Zeeman-NQR A\m\= +1 transitions for half-integer spin from 3/2 and 7/2 are derived using an optimized (6, (j)) sampling algorithm for the intensity response. The 1 = 3/2 system is examined over the full asymmetry range, whereas the I >3/2 lineshapes are calculated for rj^0.35. The algorithm adopted is modelled on the concepts in the earlier NMR lineshape calculations of Alderman, Solum, and Grant**. 
  Reference    Z. Naturforsch. 45a, 550—558 (1990); received August 23 1989 
  Published    1990 
  Keywords    NQR, Zeeman, quadrupole, powder, lineshape 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0550.pdf 
 Identifier    ZNA-1990-45a-0550 
 Volume    45 
4Author    G. B. Furman, G. E. Kibrik, A. Yu, I. G. Poljakov, ShaposhnikovRequires cookie*
 Title    NQR in the Effective Fields of a Multiple-Pulse Sequence  
 Abstract    We discuss a new form of resonant response for a quadrupolar nuclear spin system subjected to applied alternating magnetic fields. 
  Reference    Z. Naturforsch. 45a, 567—569 (1990); received August 23 1989 in revised form November 24 1989 
  Published    1990 
  Keywords    NQR, Multiple-pulse, Effective field 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0567.pdf 
 Identifier    ZNA-1990-45a-0567 
 Volume    45 
5Author    Sundara Ramaprabhu, EdwinA C LückenRequires cookie*
 Title    Cu and 79 81 Br NQR Studies of Thione Complexes of Cu(I) Halides  
 Abstract    63, 65£ U NQR frequencies, together with their temperature dependence, are reported for several complexes formed between cuprous chloride or bromide and heterocyclic thiones. For bromides the 79,8fgr resonances have also been detected. These results indicate that, with one exception, the copper atom is tricoordinated by two sulphur atoms and one halogen. Several of these complexes show phase changes in the range 77-300 K. 
  Reference    Z. Naturforsch. 47a, 125—128 (1992); received July 26 1991 
  Published    1992 
  Keywords    NQR, Copper(I), Thione 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0125.pdf 
 Identifier    ZNA-1992-47a-0125 
 Volume    47 
6Author    B. C. Sanctuary, M. Angala, S. K. Rish, N. AnRequires cookie*
 Title    Theory of NQR Pulses  
 Abstract    Pulses applied to spin systems with I > 1/2 in the absence of any external fields, the NQR case, are fundamentally different from NMR pulses. In particular, both rotating and counter-rotating components of the rf field must be kept in NQR, whereas only the "in phase" component need be retained in NMR. NQR pulses are illustrated for 7 = 3 / 2 in an axially symmetric electric field gradient (EFG). 
  Reference    Z. Naturforsch. 49a, 71—7 (1994); received October 27 1993 
  Published    1994 
  Keywords    NQR, Pulse, Density matrix, NMR 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0071.pdf 
 Identifier    ZNA-1994-49a-0071 
 Volume    49 
7Author    Christovam Mendonça, SaidR. RabbaniRequires cookie*
 Title    Anharmonic Librations and the Temperature Dependence of NQR Frequencies  
 Abstract    The temperature dependence of NQR frequencies of nuclei in molecules undergoing quasi-har-monic rotational oscillations is calculated. Following the model proposed by Bayer, the instanta-neous orientation of the electric field gradient principal axes is assumed to change from its average orientation as a result of rotational oscillations, while the EFG magnitude remains constant. The eigenstates and energy eigenvalues of a rotator in a potential of the form V(0)= V 2 0 2 — K 4 0 4 are calculated by standard perturbation methods, followed by the evaluation of statistical averages of square angular amplitudes. For molecular crystals with more than one molecule in a unit cell the angular displacements are expressed in terms of normal coordinates, and the same procedure is followed. The final expression for the change in the NQR frequency consists of two terms, the first one being related to the harmonic part of the potential and the second one to the quartic term. At the absolute zero it yields a nonzero contribution to <ö 2 >, and for high temperatures it reproduces the nonlinear character of v Q (T) observed experimentally. The model has been tested with measure-ments on solid Cl 2 performed by Nakamura and Chihara, combined with libration mode frequencies measured in Raman spectroscopy by Cahill and Leroi and analysed according to our anharmonic libration picture. The fitting of our equation to experimental data supports Cahill and Leroi's hypothesis about the existence of an undetected libration mode in Cl 2 Raman spectra of frequency near 60 cm" 
  Reference    Z. Naturforsch. 51a, 698—704 (1996); received November 20 1995 
  Published    1996 
  Keywords    NQR, Bayer's Model, Anharmonic Vibrations 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0698.pdf 
 Identifier    ZNA-1996-51a-0698 
 Volume    51 
8Author    IgorA. KyuntselRequires cookie*
 Title    C1 NQR Study of Thermoactivated Motions of Nitro Groups in Picryl Chloride  
 Abstract    The temperature dependences of the 35 C1 NQR frequency (v), spin-lattice relaxation time (T^), and spin-spin relaxation time (T 2) have been studied in 2,4,6-trinitrochlorobenzene (picryl chloride) from 77 K up to the melting point (354 K). The 7\ (T) curve exhibits a pronounced composite mimimum near 300 K which gives evidence for the reorientations of the two ort ho-N0 2 groups around their two-fold symmetry axes with the activation energies of 27.4 kJ mol 1 and 31.2 kJ mol 1 . These values can be related to the ortho-N0 2 groups having the twist angles of 33° and 81°, respectively (the crystal structure of picryl chloride is known). The T 2 (T) dependence exhibits interesting features, too: a deep minimum about 140 K and a new rapid decrease above 270 K. 
  Reference    Z. Naturforsch. 51a, 713—715 (1996); received October 10 1995 
  Published    1996 
  Keywords    NQR, reorientation motion, nitro group 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0713.pdf 
 Identifier    ZNA-1996-51a-0713 
 Volume    51 
9Author    PhilipJ. Bray, GaryL. PetersenRequires cookie*
 Title    NMR and NQR Studies of Borate Glasses  
 Abstract    Nuclear magnetic resonance (NMR) has been used for some 40 years to study atomic arrange-ments, chemical bonding, and structural groupings in borate glasses and crystalline compounds, and nuclear quadrupole resonance (NQR) has more recently increased the resolution and accuracy of the measurements. Examples are presented of the use of first-order and second-order quadrupo-lar effects in "B NMR spectra to obtain structural information, and n B and 10 B NQR spectra to obtain the quadrupolar parameters Q cc (the coupling constant) and 77 (the asymmetry parameter) with accuracies of 5 or 6 significant figures, and 3 figures, respectively. Q cc and 77 are extremely sensitive to changes in atomic rearrangements and chemical bonds, so they are excellent monitors and provide identification of bonding configurations and structural groupings in borates: Examples are also presented in which combinations of NMR and NQR data are used to extract the desired information. NQR detection of resonances at frequencies as low as 276 kHz is discussed. 
  Reference    Z. Naturforsch. 53a, 273—284 (1998); received December 30 1997 
  Published    1998 
  Keywords    NMR, NQR, Borates, Quadrupolar Interactions 
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 TEI-XML for    default:Reihe_A/53/ZNA-1998-53a-0273.pdf 
 Identifier    ZNA-1998-53a-0273 
 Volume    53 
10Author    Maria Zdanowska-Fnjczek, Malgorzata Grottel, Ryszard JakubasRequires cookie*
 Title    C1 NQR and l H NMR Studies of Molecular Motions in Guanidinium Salt of Chloroacetic Acid  
 Abstract    Multinuclear NQR and NMR techniques have been applied in order to study the molecular dynamics in [C(NH 2) 3 ](ClH 2 CCOO). The 35 C1 NQR frequency was measured over a wide range of temperature. The experimental results were described by using the theories of Bayer and Brown which take into account the torsional oscillations of the CClH 2 -group of the anion. A study of the proton NMR second moment as well as relaxation times T, and T Xp performed in a wide temperature range revealed an onset of the guanidinium cation reorientation around its two-fold symmetry axis. Activation parameters for this motion were determined. 
  Reference    Z. Naturforsch. 53a, 484—487 (1998); received March 24 1998 
  Published    1998 
  Keywords    NMR, NQR, Molecular Motion 
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 TEI-XML for    default:Reihe_A/53/ZNA-1998-53a-0484.pdf 
 Identifier    ZNA-1998-53a-0484 
 Volume    53 
11Author    G. J. Hill, J. M. Keartland, M.J R HochRequires cookie*
 Title    Pressure Dependence of the EFG in Semimetallic Arsenic and Antimony  
 Abstract    The pressure variation of the axial EFG at the ion sites in semimetallic arsenic and antimony, at am-bient temperature, has been investigated using pulsed NQR. A weakly nonlinear decrease of the EFG is observed in both systems. The data are analyzed in terms of the lattice contribution to the EFG, which involves a lattice of point monopoles immersed in a uniform, compensating, background charge. The pressure dependence of the EFG obtained from the present measurements is far weaker than the pres-sure dependence of the calculated lattice contribution. Our results support previous suggestions that va-lence effects are important in determining the EFG in these semimetals. 
  Reference    Z. Naturforsch. 53a, 501—503 (1998); received March 24 1998 
  Published    1998 
  Keywords    EFG, NQR, Arsenic, Antimony, Pressure 
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 TEI-XML for    default:Reihe_A/53/ZNA-1998-53a-0501.pdf 
 Identifier    ZNA-1998-53a-0501 
 Volume    53 
12Author    G. B. Furman, S. D. Goren, A. M. Panich, A. I. ShamesRequires cookie*
 Title    Spin Diffusion in Pure Multiple-Pulse NQR  
 Abstract    We present a detailed theoretical and experimental NQR multiple-pulse spin-locking study of spin-lattice relaxation and spin diffusion processes in the presence of paramagnetic impurities in solids. The obtained diffusion equation was obtained allows to find the time dependence of the magnetization in the effective field. The spin lattice relaxation times were calculated, both for direct and diffusion regimes, as functions of the correlation time and multiple-pulse parameters. Measurements of relaxation times in rotating frame allow to determine the diffusion coefficient and the radius of the diffusion barrier in 7-irradiated polycrystalline samples of NaCIO}. 
  Reference    Z. Naturforsch. 55a, 54—60 (2000); received August 25 1999 
  Published    2000 
  Keywords    NQR, Paramagnetic Impurities, Spin Diffusion 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0054.pdf 
 Identifier    ZNA-2000-55a-0054 
 Volume    55 
13Author    Masao Hashimoto, Akiko Shono, Yoshiyuki Mido, Haruo Niki, Hiroshi Hentona, Koichi ManoRequires cookie*
 Title    Narrowing of the 3 5 CI NQR Lines of Trichloroacetamide Caused by Its Ferroelectric Phase Transition  
 Abstract    Dielectric measurements on single crystals and DSC of the title compound (monoclinic, space group P2 X) revealed a ferroelectric transition at ca. 355 K (AH xs 0.5 kJ mol"Powder x-ray diffraction indicated that the high temperature phase is also monoclinic and the change in volume at the transition is very small. A displacement of hydrogen atoms is considered as responsible for the appearance of ferroelectricity. The 35 C1 NQR signals at ca. 77 K were considerably broad, but a drastic narrowing took place after the compound had once experienced the phase transition. A tentative assignment of the NQR spectrum was made from a calculation of the NQR frequencies based on the CNDO/2 method. Another phase transition was evidenced by a small drift of the DSC curve and a slight anomaly of the dielectric behavior around 358 K. The present *H NMR experi-ments gave no indication of the onset of torsional motion of the NH 2 group reported to occur at ca. 210 K. 
  Reference    Z. Naturforsch. 45a, 327—333 (1990); received August 26 1989 in revised form November 1 1989 
  Published    1990 
  Keywords    NQR, Phase transition, Ferroelectricity, Hydrogen bond, Disordered structure 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0327.pdf 
 Identifier    ZNA-1990-45a-0327 
 Volume    45 
14Author    J. Pirnat, J. Lužnik, Z. Trontelj, P. K. KadabaRequires cookie*
 Title    Iodine NQR and Phase Transitions in [N(CH 3 ) 4 ] 2 ZnI 4 * a  
 Abstract    Using a superregenerative NQR spectrometer, the temperature dependence of 127 I NQR spectra in [N(CH 3) 4 ] 2 ZnI 4 was measured between 167 and 335 K. The measurements confirm two known structural phase transitions at 219 and 257.5 K. The correspondence between the distinct regions of iodine NQR spectra and the crystal structure is discussed. The relation of [N(CH 3) 4 ] 2 ZnI 4 to the incommensurate family with the general formula X 2 YZ 4 and the high temperature (paraphase) crystal space group D^ (Pmcn) is studied. 
  Reference    Z. Naturforsch. 45a, 349—352 (1990); received August 23 1989 in revised form 25 November 1989 
  Published    1990 
  Keywords    NQR, phase transitions, ferroelectric, crystal structure, displacement modulation 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0349.pdf 
 Identifier    ZNA-1990-45a-0349 
 Volume    45 
15Author    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 
16Author    H. Nishihara, K. Hayashi, M. Naito, T. Butz, A. Lerf, S. SaibeneRequires cookie*
 Title    NQR and Low-Field NMR of 181 Ta in the Low-Temperature CDW State of 2 H-TaS 2  
 Abstract    NQR and low-field NMR spectra of 18I Ta are reported to probe the electronic environment of inequivalent tantalum sites in the low-temperature CDW state of a layered compound 2 H-TaS 2 . The overall features are found to be consistent with the structure consisting of nine-atom snowflake clusters in a locally commensurate CDW state. 
  Reference    Z. Naturforsch. 45a, 412—414 (1990); received August 23 1989 
  Published    1990 
  Keywords    NQR, NMR, 181 Ta, CDW, TaS 2 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0412.pdf 
 Identifier    ZNA-1990-45a-0412 
 Volume    45 
17Author    Y. Nakamichi, K. Kumagai, H. Nakajima, T. FujitaRequires cookie*
 Title    63/65 Cu _ N Q R Study of i m p ur ity-lnduced Magnetic Order in YBa 2 (Cu 1 _ x M x ) 3 0 7 (M = Fe, Co)  
 Abstract    We have studied 63 ' 65 Cu NQR at the Cu(l)-chain and Cu(2)-plane site of YBa 2 (Cu!_ X M X) 3 0 7 (M = Fe, Co). The spin-lattice relaxation rate, Tj -1 , is enhanced at low temperatures and has in the Fe-system a peak at 2 and 4 K for x = 0.005 and 0.015, respectively. Below the peak temperatures the intensity of the Cu-NQR signal decreases rapidly. The results suggest that magnetic ordering of either Fe or Cu moments occurs without destroying the superconductivity below T c on substituting Cu by magnetic ions. superconductor, YBa 2 (Cu 1 _ ;t Fe JC)30 7 . 
  Reference    Z. Naturforsch. 45a, 423—428 (1990); received September 141989 in revised version December 11989 
  Published    1990 
  Keywords    NQR, Magnetic order, High-T c 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0423.pdf 
 Identifier    ZNA-1990-45a-0423 
 Volume    45 
18Author    Haruo Niki, Ryokan Igei, Takuya Higa, Masao Hashimoto, Takahiro IsonoRequires cookie*
 Title    Lattice Imperfections and Relaxation of Cl NQR in Chloral Iso-Butylhemiacetal  
 Abstract    The temperature dependence of the S/N ratios of three 35 C1 NQR lines (v l5 v 2 , v 3) in chloral iso-butylhemiacetal shows interesting features in the range 77-300 K. 35 C1 T y indicates that above 220 K reorientation of CC1 3 is excited, and this results in a gradual decrease in S/N. The activation energy calculated from 35 C1 NQR T l results is 30 kJ mol -1 for v x and v 2 but 25 kJ mol -1 for v 3 . The difference seems to be attributable to the motion of H in the OH group. A minimum of 35 C1 NQR T 2 is found around 180 K but 35 C1 T\ shows no anomaly. 35 C1 T 2 determines the S/N ratios in the range between 130-220 K. The line broadening below 130 K is attributable to an inhomo-geneity of the electric field gradient at resonant nuclei produced by lattice defects. 
  Reference    Z. Naturforsch. 45a, 481—484 (1990); received August 26 1989 
  Published    1990 
  Keywords    NQR, Lattice imperfections, Magnetic relaxation, Hydrogen bonding 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0481.pdf 
 Identifier    ZNA-1990-45a-0481 
 Volume    45 
19Author    G. B. FurmanRequires cookie*
 Title    Bloch-Siegert Effect in Pure Nuclear Quadrupole Resonance  
 Abstract    The Bloch-Siegert shift of the NQR frequency is calculated for the case when more than one resonance transition are excited by radiofrequency fields. 
  Reference    Z. Naturforsch. 45a, 565—566 (1990); received August 23 1989 in revised form November 24 1989 
  Published    1990 
  Keywords    NQR, Bloch-Siegert shift, Radiofrequency field 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0565.pdf 
 Identifier    ZNA-1990-45a-0565 
 Volume    45 
20Author    Motohiro Mizuno, Tetsuo Asaji, Atsushi Tachikawa, The Late, Daiyu NakamuraRequires cookie*
 Abstract    h lo r in e N Q R S p in -L a ttic e R e la x a tio n a n d E le c tro n S p in D y n a m ic s in P a r a m a g n e tic [ C o (H 20) 6] I P tC l 6| Chlorine NQR spin-lattice relaxation times T1Q were determined for [Co(H,0)6][PtCl6] at 4.2 400 K. Above ca. 350 K, T1Q decreased rapidly showing the onset of a reorientation of [PtCl6]2-. The activation energy Ea of this reorientation was determined as 125 ± 15 kJ mol ~1. With decreasing temperature, Tlfi showed a maximum at ca. 250 K. Below ca. 200 K, Tl(. is governed by the magnetic dipolar interaction between chlorines and paramagnetic Co2+ ions and is inversely proportional to the electron spin correlation time re of Co2 . Te is shown to be determined by the electron spin-lattice relaxation time Tle and the temperature independent correlation time rs for the spin-exchange between neighbouring ions above and below ca. 50 K, respectively. The temperature dependence of Tle is explained by assuming the Orbach process with an energy gap A/k of 530 + 20 K as Tle = 5 x 10~14 exp(530/T)s. ts was estimated to be 0.9 x 10"10 s. The temperature dependence of the ESR linewidth of Mn2+ impurities in single crystal was also measured, intending to study Co2+ spin dynamics. The limit of the ESR method is discussed by comparing the obtained results with those of the NQR method. 
  Reference    Z. Naturforsch. 46a, 1103 (1991); received September 17 1991 
  Published    1991 
  Keywords    Spin-lattice relaxation, NQR, ESR, Reorientation, Orbach process 
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 TEI-XML for    default:Reihe_A/46/ZNA-1991-46a-1103.pdf 
 Identifier    ZNA-1991-46a-1103 
 Volume    46