Tb-doped glasses usually show a paramagnetic character. Recently, glasses h
ave been successfully doped with Tb3+ ions in heavy concentrations of more
than 10 at. %. These glasses show magnetic properties different from the co
nventional paramagnetic behavior. However the mechanism of their anomalous
magnetic properties has not been clarified yet. In this study, we prepared
heavily Tb-doped glasses and investigated their magnetic and magneto-optica
l properties. We observed some results that indicate a slower relaxation pr
ocess of more than 1.0 sec.