Temperature dependence of the spin dynamics in the strongly frustrated antiferromagnet SrCr9xGa12-9xO19

We have used neutron scattering, with and without polarization analysis, to examine the magnetic #uctuations of SrCr9xGa12~9xO19 in a wide dynamic range from 0.001 to 10 meV at temperatures from 0.1 to 300 K. Below the macroscopic freezing temperature (+4 K), an elastic response with a broadly peaked Q-dependence prevails, and the dynamic response is only weakly temperature dependent. Above the freezing temperature the response becomes quasi-elastic and obeys, for +u(5 meV, a scaling behaviour suggesting a disorder dominated critical regime quite di!erent from that of a standard paramagnet.