LOW FIELD AC MAGNETIC SUSCEPTIBILITY MEASUREMENTS OF MANGANESE ALUMINOSILICATE GLASSES

The magnetic susceptibility of MnO.Al 2 O 3 .SiO 2 spin glasses has been measured over a temperature range of 1.5–150 K using a low-field ac mutual inductance technique. The measuring frequency was 250 Hz with a field of 417 mOe (peak). The Mn concentration varied from 6 to 19 atomic percent (at %). At temperatures above 70 K, the susceptibilities follow a Curie-Wiess behavior with a negative Curie temperature and a Bohr magneton number corresponding nearly to the free ion value of Mn. However, below 70 K all glass samples show strong deviation from the Curie-Wiess behavior (a decrease in 1/χ), culminating in spin glass susceptibility maxima at liquid helium temperature for Mn concentration above 9 at %. These results suggest the formation of antiferromagnetic cluster which grows in size with decreasing temperature and becomes infinitely large as the spin glass freezing temperature is approached.