We report the direct observation of the effects of quenched disorder on the critical behavior of partially frustrated amorphous FeMnZr alloys by the systematic analysis of high-precision ac susceptibility data and dc magnetization data. Interestingly, the analysis reveals that the presence of short-range quenched disorder does not alter the actual critical behavior. However, it does affect quantities such as the Curie temperature, the peak value of effective exponent $\gamma$, width of the peak, and crossover temperatures. The observed temperature dependence of the effective critical exponent can be understood in terms of the field-theoretical renormalization group approach. Also, the present results would help in identifying the main source of the spread in the exponent values reported in the literature.

• Received 17 May 2003

DOI:https://doi.org/10.1103/PhysRevLett.91.137202