Article

Quadrupole spin-echo envelopes for Bi4Ge3O12 single crystals doped with the atoms of transition and rare-earth elements

JETP Letters (impact factor: 1.35). 04/2012; 86(5):337-339. DOI:10.1134/S0021364007170122 pp.337-339

ABSTRACT The influence of a weak (below 50 Oe) constant magnetic field on a quadrupole spin-echo envelope was studied for an undoped
single crystal Bi4Ge3O12, in which local magnetic fields on the order of 20–30 G were previously found, as well as for single Bi4Ge3O12 crystals doped with the atoms of transition and rare-earth elements. In all of these cases, the spin-echo envelopes were
strongly influenced. A considerable increase in the nuclear spin-spin relaxation time T
2 was observed for the undoped sample upon the switching of weak external magnetic fields. For the doped samples, the spin-echo
envelope decay became much slower already in the zero field. The external magnetic fields exhibited a markedly weaker influence
on the spin-echo envelope for the doped samples.

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    Article: Anomalous magnetism and 209 Bi nuclear spin relaxation in Bi 4 Ge 3 O 12 crystals
    V G Orlov, E A Kravchenko, Tetsuo Asaji, G S Sergeev, Yu F Kargin, · O S Volkova, · A N Vasil 'ev, T Asaji
    [show abstract] [hide abstract]
    ABSTRACT: The quadrupole 209 Bi spin–spin and spin–lattice relaxation were studied within 4.2–300 K for pure and doped Bi 4 Ge 3 O 12 single crystals which exhibit, as was previously found, anomalous magnetic properties. The results revealed an unexpectedly strong influence of minor amounts of paramagnetic dopants (0.015– 0.5 mol.%) on the relaxation processes. Various mechanisms (quadrupole, crystal electric field, electron spin fluctuations) govern the spin–lattice relaxation time T 1 in pure and doped samples. Unlike T 1 , the spin–spin relaxation time T 2 for pure and Nd-doped samples was weakly dependent on temperature within 4.2–300 K. Doping Bi 4 Ge 3 O 12 with paramagnetic atoms strongly elongated T 2 . The elongation, although not so strong, was also observed for pure and doped crystals under the influence of weak (∼30 Oe) external magnetic fields. To confirm the conclusion about strong influence of crystal field effects on the temperature dependence of al. T 1 in the temperature range 4.2–77 K, the magnetization vs. temperature and magnetic field was measured for Nd-and Gd-doped Bi 4 Ge 3 O 12 crystals using a SQUID magnetometer. The temperature behavior of magnetic susceptibility for the Nd-doped crystal was consistent with the presence of the crystal electric field effects. For the Gd-doped crystal, the Brillouin formula perfectly fitted the curve of magnetization vs. magnetic field, which pointed to the absence of the crystal electric field contribution into the spin–lattice relaxation process in this sample.
  • Source
    Article: Anomalous magnetism and 209Bi nuclear spin relaxation in Bi4Ge3O12 crystals
    V. G. Orlov, E. A. Kravchenko, Tetsuo Asaji, G. S. Sergeev, Yu. F. Kargin, O. S. Volkova, A. N. Vasil’ev
    [show abstract] [hide abstract]
    ABSTRACT: The quadrupole 209Bi spin–spin and spin–lattice relaxation were studied within 4.2–300K for pure and doped Bi4Ge3O12 single crystals which exhibit, as was previously found, anomalous magnetic properties. The results revealed an unexpectedly strong influence of minor amounts of paramagnetic dopants (0.015–0.5mol.%) on the relaxation processes. Various mechanisms (quadrupole, crystal electric field, electron spin fluctuations) govern the spin–lattice relaxation time T 1 in pure and doped samples. Unlike T 1, the spin–spin relaxation time T 2 for pure and Nd-doped samples was weakly dependent on temperature within 4.2–300K. Doping Bi4Ge3O12 with paramagnetic atoms strongly elongated T 2. The elongation, although not so strong, was also observed for pure and doped crystals under the influence of weak (∼30Oe) external magnetic fields. To confirm the conclusion about strong influence of crystal field effects on the temperature dependence of T 1 in the temperature range 4.2–77K, the magnetization vs. temperature and magnetic field was measured for Nd- and Gd-doped Bi4Ge3O12 crystals using a SQUID magnetometer. The temperature behavior of magnetic susceptibility for the Nd-doped crystal was consistent with the presence of the crystal electric field effects. For the Gd-doped crystal, the Brillouin formula perfectly fitted the curve of magnetization vs. magnetic field, which pointed to the absence of the crystal electric field contribution into the spin–lattice relaxation process in this sample. KeywordsBismuth oxy compounds–Anomalous magnetic properties–Local magnetic fields–Nuclear quadrupole spin–lattice and spin–spin relaxation
    Hyperfine Interactions 04/2012; 197(1):65-70. · 0.21 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.

Keywords

cases
 
considerable increase
 
doped samples
 
external magnetic fields exhibited
 
local magnetic fields
 
markedly weaker influence
 
nuclear spin-spin relaxation time T
 
quadrupole spin-echo envelope
 
rare-earth elements
 
single Bi4Ge3O12 crystals doped
 
undoped sample
 
weak
 
weak external magnetic fields
 
zero field
 

E A Kravchenko