Low-temperature transport of magnetic excitons in the quasi-one-dimensional antiferromagnet CsMnCl3 center dot 2H(2)O doped with Cu2+ ions

The emission decay kinetics and relative quantum yields of exciton luminescence of Cu2+-doped (3%) quasi-one-dimensional antiferromagnetic crystals CsMnCl3 . 2H(2)O have been studied in the temperature range from 4.2 to 77 K. The experimental emission decay curves have been approximated by the calculated curves obtained using computer simulation of incoherent excitons motion. The model assumes a slow interchain hopping process and a rapid intrachain migration of excitons. Exciton hopping (W) and trapping (U) rates at 4.2-77 K have been defined. A decrease of both U and W rates has been observed with a temperature lowering. The proposed model of exciton migration and trapping considered excitation passing potential barriers between Mn2+-Mn2+ and Mn2+-Cu2+ ions. To describe the deviation of U(T) and W(T) dependences from the Arrhenius law we suppose that excitons pass barriers by both hopping over it and tunneling. The energies and shapes of the barriers have been estimated. The tunneling processes were taken into account while determining the barriers energy. The role of both the exciton-phonon interaction in CsMnCl3 . 2H(2)O and the spin forbiddeness of the low-temperature (T less than or equal to 30 K) exciton migration along a chain due to the antiferromagnetic spin ordering has been discussed.