MAGNETIC-PROPERTIES OF LA(FEXAL1-X)13 AMORPHOUS-ALLOYS

Several kinds of La(Fe(x)Al1-x)13 (0.80 less-than-or-equal-to x less-than-or-equal-to 0.95) amorphous alloys have been prepared by high-rate DC sputtering to investigate the magnetic properties. The magnetic phase diagram has been established by DC and AC magnetic field measurements. Above x = 0.85, re-entrant spin-glass behaviour has been observed in the concentration range where antiferromagnetic order occurs in the crystalline state. The high-field susceptibility in this concentration range is extremely large and the magnetization curves are not easily saturated. The magnetic moment estimated from the magnetization curves measured up to 380 kOe in pulsed magnetic fields shows a maximum around x approximately 0.85, corresponding to 80 at.% Fe. The Curie temperature in the amorphous state decreases with increasing x and it is higher than the Neel and Curie temperatures in the crystalline state. The spin-wave stiffness constant in the amorphous state is extremely small, suggesting a magnetic instability.