Dynamics of the Magnetic Susceptibility of Fe $_{x}$ Al $_{100 - {\rm x}} ({\rm x} = 70, 71)$ Allo

The magnetic dynamics of Fe₇₁ Al₂₉(x = 71) and Fe₇₀ Al₃₀(x = 70) are analyzed. The alloys have been prepared by milling and further annealing. AC-susceptibility has been measured from 5 K to 300 K at several frequencies between 100 and 10 kHz with an alternating field of 0.1 Oe. In x = 70, additional susceptibility data fixing the frequency to 500 Hz and varying the field between 0.1 les h les 10 Oe were obtained. The results display real components similar to those reported in DC-magnetization, with two transitions in x = 70 and a single transition in x = 71. The complex component is much more clear with a well-defined peak for the low temperature transition ascribed to a spin freezing. The frequency variation gives 0.078(5) in x = 70 and critical zv = 7.2(5) and 0.066(9) and zv = 9.8(5) for x = 71, related to a cluster glass behavior. However the parameter beta ap 1 for both alloys which is high in the framework of a conventional slowing down. This is related to the clustered nature of the magnetic structure lacking of defined interfaces.