Experiments on the field and frequency dependence of ac susceptibility (acs) for an amorphous Fe80Mn10Zr10 alloy in the temperature range from 12 to 300 K are used to explore magnetic nature. There is a well-resolved frequency dependent maximum in the imaginary component of the acs at low temperature, which is the real significance of the reentrant spin-glass phase dynamics. The dynamic scaling analysis of the low field acs data indicates the presence of spin-glass transition TSG=40 K with a critical exponent Ψ=6.5 which seems to be a mixed state rather than a pure spin-glass state. The existence of mixed magnetic state could be understood based on exchange frustration model. © 2001 Elsevier Science B.V. All rights reserved.