CLUSTER GLASS-LIKE BEHAVIOR OF THE DILUTED ANTIFERROMAGNET FEXMG1-XTIO3 (X=0.2, X=0.3)

A diluted antiferromagnet FexMg1-xTiO3 has been shown to behave as a spin glass (x = 0.2) and a reentrant spin glass (x = 0.3) near the Fe percolation concentration x approximately 0.25. In order to obtain microscopic information on these samples, we performed Mossbauer measurements. At considerably higher temperatures than the transition temperatures, magnetically broadened spectra appear superimposed upon the paramagnetic doublets. A remarkable feature is that the intensity of the magnetic spectra increases accompanying the decrease of their linewidth. This behavior can be ascribed to the gradual slow-down of fluctuations of the antiferromagnetic clusters formed at high temperatures. To investigate the temperature variations of the relaxation time tau of the clusters, we analyzed the Mossbauer spectra using the method formulated by Blume. It has been shown that tau becomes long with decreasing temperature and the rate of the slow-down of tau is hastened around T(SG) and T(N).