ZhETF, Vol. 137,
p. 336 (February 2010)
(English translation - JETP,
Vol. 110, No. 2,
available online at www.springer.com
NUCLEAR QUADRUPOLE SPIN-LATTICE RELAXATION IN Bi4 Ge3 O12 SINGLE CRYSTALS DOPED WITH ATOMS OF d OR f ELEMENTS. CRYSTAL FIELD EFFECTS IN COMPOUNDS EXHIBITING ANOMALOUS MAGNETIC PROPERTIES
Orlov V.G., Sergeev G.S., Tetsuo Asaji, Kravchenko E.A., Kargin Yu.F.
Received: August 19, 2009
The nuclear quadrupole spin-lattice relaxation was studied in the range 4.2-300 K for single crystals of Bi4 Ge3 O12 doped with minor amounts (the tenth fractions of mol%) of paramagnetic atoms of Cr, Nd, and Gd. Unusual spin dynamic features were recently found for these crystals at room temperature: a dramatic (up to 8-fold) extension of the effective nuclear quadrupole spin-spin relaxation time T*2 occurred upon doping the pure Bi4 Ge3 O12 sample. Unlike T*2, the effective spin-lattice relaxation time T*1 at room temperature differs insignificantly for both doped and pure samples. But at lower temperatures, the samples exhibit considerably different behavior of the spin-lattice relaxation with temperature, which is caused by different contributions to the relaxation process of the dopant paramagnetic atoms. The distinctive maximum in the temperature dependence of the spin-lattice relaxation time for the Nd-doped crystal is shown to result from the crystal electric field effects.