DC and AC susceptibility measurements on Fe-SiO2 alloys have been carried o
ut from room temperature to liquid He temperature in the zero field-cooling
(ZFC) and the field-cooling (FC) mode. The magnetization in the ZFC mode i
ncreases rapidly below a characteristic temperature, T-c, and decreases bel
ow the freezing temperature, T-f, both of which depend on the applied magne
tic field, frequency and Fe concentration. A magnetic phase diagram is desc
ribed from these observations. (C) 1999 Elsevier Science B.V. All rights re
served.