An ac susceptibility study of Mn substituted amorphous FeZr alloys

The temperature dependence of the ac susceptibility of amorphous Fe90-xMnxZ r10 (x = 0, 4, 8) has been measured at different ac fields in the frequency range of 80 Hz to 1 kHz. All the compositions of the present study exhibit a double magnetic transition below room temperature. It is found that the Curie temperature (T-C) decreases while the spin-glass transition temperatu re (T-f) increases as Mn concentration increases from 0 to 8 at%. The value s of Te and critical exponent associated with the magnetic susceptibility w ere extracted from ac susceptibility measurements. The critical exponent is in close agreement with the value predicted by the three-dimensional Heise nberg model. The results obtained here can be explained on the basis of com peting exchange interactions below the magnetic ordering temperature.