Spin fluctuations in amorphous La(NixAl1-x)13 alloys consisting of icosahedral clusters

Abstract

Thermal properties of spin fluctuations have been investigated for amorphous La(NixAl1-x)13 (0.90<or=x<or=0.975) alloys. The temperature T dependence of magnetization M for the present alloys exhibits an M2-T4/3 relation below the Curie temperature TC in the La(Ni0.90Al0.10)13 amorphous alloy and its relation becomes poor with increasing Ni concentration. The inverse magnetic susceptibility shows a peculiar temperature dependence above Tc owing to the saturation of the thermal growth of spin fluctuations. The temperature dependence of the inverse magnetic susceptibility is influenced by the external magnetic field. The distribution of spin fluctuations is localized in both wavenumber and frequency space in the low-Ni-concentration range, and it becomes broader with increasing Ni concentration. The generalized Rhodes-Wohlfarth plots for the present alloy system indicate that the magnetic susceptibility is dominated by the thermal variation in spin fluctuations.