Hyperfine Interactions 122 (1999) 223–231 223 Magnetic properties of fcc (Co 95 Fe 5 ) 1-x Al x ribbons Salah A. Makhlouf a,b , F.T. Parker b and T. Benameur c a Department of Physics, Faculty of Science, Assiut University, Assiut 71516, Egypt b Center for Magnetic Recording Research, University of California at San Diego, La Jolla, CA 92093-0401, USA c D´ epartement de G´ enie M´ ecanique, Ecole National D’Ing´ enieurs De Monastir, 5019 Monastir, Tunisia Received 1 June 1998; revised 2 September 1998 Rapidly quenched (Co95Fe5)1-xAlx ribbons are investigated by X-ray diffraction, magne- tization, and M¨ ossbauer effect measurements. A single fcc phase is obtained for all ribbons x  10 at.%. The lattice constant increases linearly with x and is discussed in connection with magnetic moment. The influence of Al substitution on both magnetization and Fe-atom hyperfine field (H) is studied. At 296 K, the magnetization decreases linearly while H drops nonlinearly as x increases. Al substitution leads to substantial differences in iron hyperfine fields in bcc and fcc systems. Fe moment is perturbed differently by Al substitution in fcc (Co95Fe5)1-xAlx and bcc Fe–Al systems. 1. Introduction Magnetic properties of Al-diluted disordered ferromagnetic alloys have been widely studied in both binary [1–5] and ternary [6–8] systems. The concentration dependence of saturation magnetization in bcc Fe 1-x Al x alloys for x  15 at.% corresponds, in the limits of experimental precision, to simple dilution: the mean magnetic moment per transition metal atom ¯ μ decreases linearly with x and the slope d ¯ μ/dx = -2.2μ B equals the opposite of the moment of the iron matrix. For Co 1-x Al x , however, the magnetizations of the evaporated films were greater than bulk alloys of the same composition and the concentration dependence of ¯ μ for both of them devi- ates from the simple dilution concept [9]. M¨ ossbauer spectroscopy measurements have proved that the simple dilution concept is oversimplified and does not hold even for bcc Fe 1-x Al x alloys [4]. In particular, the corresponding quantity in that reference, the average hyperfine field H decreases much more slowly with x than ¯ μ does. Combined magnetization and M¨ ossbauer effect measurements on bcc (Fe–Ni)Al, bcc (Fe–Co)Al, and fcc (Ni–Fe)Al [6–8] indicate that Al neighbors do not change the magnetic moment of Fe atoms in any of these systems, while at the same time the magnetic moment of Ni and Co are appreciably influenced by them. Moreover, they reveal a local nature of this interaction, which is not dependent on the crystal structure. Recently, 57 Fe M¨ ossbauer effect measurements have been done on hcp (Co 99 Fe 1 ) 1-x V x alloy which because of its lattice parameters is visualized by the authors as fcc [10]. The influence  J.C. Baltzer AG, Science Publishers