Small-angle neutron-scattering studies of Ce(Fe_1-xAl _x)₂

Ce(Fe_1-xAl_x)₂, with x=0, 0.06, and 0.14, has been studied by small-angle neutron scattering in order to investigate the instability of the ferromagnetic state in the pure material to small amounts of magnetic disorder. The pure material (x=0) displays a ferromagnetic transition near T_C=225 K, and more complicated behavior below ∼100 K. The disordered alloys, x=0.06 and x=0.14, display ferromagnetic-like states over relatively narrow temperature ranges, and an additional low-temperature phase. The ferromagnetic-like state in the x=0.14 alloy appears to be qualitatively different from that exhibited by the other two. High-wave-vector-resolution measurements on the x=0.06 sample indicate that its low-temperature ordered phase is ferrimagnetic in origin.