Structure relaxations and low-field magnetic properties of the thick amorphous Fe 75 - x Al 5 P 11 Ga x B 4 C 5 ( x = 0 , 2 or 5) ribbons subjected to accumulative annealing below the crystallization temperature are investigated. From Mössbauer spectroscopy studies we have found that the average hyperfine field slighty increases after the heat treatment of the samples due to structure relaxations. The intensity of the magnetic susceptibility disaccommodation decreases with the thickness of ribbons. It may be connected with annealing out of some free volumes during the sample preparation. Moreover, we have stated that core losses of the investigated alloys are comparable with those of conventional amorphous materials.