ATOMIC STRUCTURES, MAGNETOVOLUME AND PRESSURE EFFECTS IN AMORPHOUS LA(FEXAL1-X)(13) ALLOYS CONSISTING OF ICOSAHEDRAL CLUSTERS

The atomic structures of amorphous La(FexAl1-x)(13) alloys have been i nvestigated by x-ray diffraction, and the local ordering characterized by the icosahedral clusters has been confirmed. From the Fe-57 Mossba uer spectra, it has been revealed that the local environment around Fe atoms in the amorphous La(Fe0.90Al0.10)(13) alloy is very similar to that in the crystalline counterpart. Re-entrant spin-glass behavior ha s been observed in the concentration range where the antiferromagnetic order occurs in the crystalline state. The Curie temperature in the a morphous state decreases with increasing x and it is higher than the N eel and Curie temperatures in the crystalline state. The spin-wave sti ffness constant in the amorphous state is extremely small, suggesting a magnetic instability. The amorphous RE(Fe1-xAlx)(13) alloys also exh ibit re-entrant spin-glass behavior and the spin freezing temperature is hardly changed by replacing RE because there is no change in the Fe -Fe distance in the icosahedral clusters. A large thermal expansion an omaly has been observed in a wide temperature range. This anomaly is r etained, even at high temperatures well above T-c. A significant Delta E effect has also been found in the temperature and field dependences of Young's modulus. The temperature dependence of the forced-volume m agnetostriction partial derivative omega/partial derivative H exhibits a broad peak at the spin freezing temperature T-f and its divergent b ehavior at T-f is accounted for by the variable amplitude of the local magnetic moment in the itinerant spin glasses. The temperature depend ence of the saturation magnetostriction lambda(S) of the ferromagnetic alloys is explained by the two-ion model, reflecting the peculiar amo rphous structure consisting of icosahedral clusters. Poisson's ratio d etermined from the surface phase velocities of the Rayleigh and Sezawa waves is very close to 1/3. The compressibility kappa obtained from B rillouin scattering is significantly large. Various magnetovolume and pressure effects become remarkable with increasing Fe content.