We present theoretical studies on the spin diffusion dynamics of the double
exchange model including Jahn-Teller distortion for manganites. It is show
n that due to the trapping of composite polarons in the magnetic transition
regime, the spin diffusion dynamics becomes important. The spin diffusion
coefficient obtained by our theory agrees well with experimental data. (C)
2000 American Institute of Physics. [S0021-8979(00)32008-4].