Temperature dependence of the spin dynamics in the strongly frustrated antiferromagnet SrCr9xCa12-9xO19 (SCGO)

We have used neutron scattering, with and without polarization analysis, to examine the magnetic fluctuations of SrCr9xCa12-9xO19 in a wide dynamic ra nge from 0.001 to 10 meV at temperatures from 0.1 to 300 K. Below the macro scopic freezing temperature( approximate to 4 K), an elastic response with a broadly peaked Q-dependence prevails, and the dynamic response is only we akly temperature dependent. Above the freezing temperature the response bec omes quasi-elastic and obeys, for h omega < 5 meV, a scaling behaviour sugg esting a disorder dominated critical regime quite different from that of a standard paramagnet. (C) 2000 Elsevier Science B.V. All rights reserved.