205Tl-NMR on Tl2SeO4

Abstract

205Tl-NMR absorption lines in the Tl2SeO4 crystal have been measured below room temperature. We have observed the remarkable changes in the resonance position and line width of the 205Tl-NMR absorption line at TII–III = 97 K and TIII–IV = 74 K. It is also found that the large shift of the resonance position and with decreasing temperature the drastic increase of the line width of the 205Tl-NMR absorption line are observed even in the temperature range from 74 K to 97 K (phase III). Moreover below TII–III we have observed the anomalous 205Tl-NMR absorption lines with two peaks in both tails, although above TII–III the NMR absorption line is described by the single Gaussian curve. In addition, it is found that the positions of two peaks change even in the phase III. These results imply that the Tl2SeO4 crystal shows the structural incommensurate modulation in the phase III, as observed in many A2BX4 type crystals (A = K, Rb, Cs, NH4, N(CH3)4; B = Zn, Co, Se, S; X = Br, Cl, O).