The ESR spectrum of Dy3+ ion in the low-symmetry RbDy(WO4)(2) crystal
has been studied in the temperature region of T = 4.2 divided by 30 K.
The ESR linewidth was found to increase from 130 mT up to the maximum
value of 190 mT at T = 9 It and then to decrease down to 150 mT at 4.
2 K. The components of the g-tensor change considerably without change
of their spatial orientation in the temperature range from 12 K to 7
K: g(z) = 2.5, g(x) approximate to 0, g(y) = 1.41 at T > 12 K; g(z) =
1.53, g(x) approximate to 0, g(y) = 1.2 at T < 7 K. The observed X-sha
ped behaviour of absorption linewidth and the decrease in the g-factor
are assumed to be due to the low-temperature structural phase transit
ion (T-SPT approximate to 9 K) The width of the transition area is of
about 5 K. It is suggested that the symmetry of high- and low-temperat
ure phases is identical.