Spin freezing in the Kagomé system SrCr8Ga4O19 - high resolution study of the elastic and low-energy dynamic responses

The magnetic response of the SrCr8Ga4O19 compound has been examined using the backscattering instrument IN16 at the ILL, in the temperature range from 100 mK up to 20 K. Both the standard conÞguration with an energy resolution of E 1 micro eV, and the polished monochromator conÞguration with E 0.4 micro eV were used to examine the response in an energy window extending to 14 micro eV. Additional data taken on IN5 have been used to investigate the e¤ect of the energy resolution width on the observed ÔelasticÕ signal. The apparent transition temperature becomes independent of the resolution for *E(1 leV, and with a resolution of *E"0.4 leV there is no detectable broadening of the elastic peak at temperatures below about T)2 K. Our observations are in overall agreement with the earlier results on the elastic response, confirm the freezing of about 15 of the total Cr (S"32) moment and push the time scale of the frozen configuration into the 0.1 ls range.