An ac Susceptibility Study of Mn Substituted Amorphous FeZr Alloys

The temperature dependence of the ac susceptibility of amorphous Fe 90-x Mn x Zr 10 (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 temperature (T f ) increases as Mn concentration increases from 0 to 8 at%. The values of T c and critical exponent associated with the magnetic susceptibility were extracted from ac susceptibility measurements. The critical exponent is in close agreement with the value predicted by the three-dimensional Heisenberg model. The results obtained here can be explained on the basis of competing exchange interactions below the magnetic ordering temperature.