A CRITICAL ASSESSMENT OF CONTINUOUS SATURATION METHOD FOR MEASURING ELECTRON SPIN-LATTICE RELAXATION TIMES IN PRESENCE OF A PHONON BOTTLENECK

A comparison is made between the spin-lattice relaxation times calculated in various ways from continuous saturation measurements and those obtained using the conventional pulse saturation method at 9·27 GHz, over the temperature range 1·7-4·2°K. The material investigated was [(C4H9)4N]2 Cu[S2C 2(CN)2]2 for which pulse saturation measurements were available. The conclusion is drawn that, whereas relative measurements compare very favourably, it is difficult to ascribe an absolute value to T1 because of the uncertainty inherent in the values of ancillary parameters (e.g. H1 and T2) and the assumptions made concerning the spin system. The forms of the saturation curves obtained using this material are found to agree closely with those calculated from the steady state solutions to the bottlenecked rate equation. The difficulties involved in the interpretation of such data under bottleneck conditions are discussed.