ELECTRON-SPIN ECHO STUDIES OF FLIPPING TYPE MINIMUM IN PHASE MEMORY TIME OF CU(II) IONS IN TRIGLYCINE SELENATE CRYSTAL AT LOW-TEMPERATURES

Electron spin phase memory time TM characterizing a destroying of prec ession motion phase coherence of the spins excited by microwave pulses was studied in copper(II) doped triglycine selenate (TGSe) crystal in the temperature range 4.2-110 K for a selected single crystal orienta tion where nearly whole EPR spectrum of Cu(II) can be excited. TM vari es strongly with temperature and exhibits a minimum at about 55 K. The decrease of T-M from 1200 ns at 25 K to 200 ns at 100 K reflects a co ntinuous spin packet broadening due to spectra diffusion processes. Th e minimum results from a resonance shortening of T-M by a molecular mo tion with E(a) = 0.24 kcal mol(-1) = 1.0 kJ mol(-1) and tau(c) = 3.8 x 10(-6) s at 55 K. We identified this motion as a flipping of the glyc ine GI between two orientations in the crystal unit cell, which also d etermines the spontaneous polarization value in the ferroelectric phas e of the crystal. Copyright (C) 1996 Elsevier Science Ltd