Dynamics of random spin systems

We present inelastic neutron scattering experiments on three prototypical random magnets. For the dilute, insulating antiferromagnet Rb2Co/sub c/Mg/sub 1-c/F4, the randomness has purely geometrical consequences, and the anomalous dynamical behavior which we observe for c close to the magnetic percolation threshold is due to the fractal nature of percolating networks. Comparison of inelastic and quasielastic scattering data demonstrate the dynamical nature of the spin glass transition in amorphous, metallic MnSi. Finally, we show the coexistence of spin waves and static spin fluctuations near the crossover from ferromagnetic to spin glass behaviors in amorphous (Fe/sub x/Mn/sub 1-x/)75P16B6Al3