Magnetic behaviour in amorphous TbxCu1−x alloys (x = 0.18, 0.22, 0.33, 0.50 and 0.65)

The results of susceptibility, magnetization and small-angle neutron scattering measurement for 4 K < T < 300 K are discussed. In all cases the magnetization is distributed in an inhomogeneous way either inside isolated bubbles or within the interbubble spaces. The terbium-poor alloys present a usual hysteresis loop contrary to the terbium-rich alloys for which the applied field plays an important role in establishing the moment order. The order established in a high field (H ≈ 3.6 × 10⁶ A m⁻¹) is preserved when this field decreases or is reversed. Polishing increases the volume of the magnetic domains within the sample and orients the moments at the surface perpendicular to the polishing direction.

The magnetic susceptibility in a 1.6 × 10⁵ A m⁻¹ field and the isothermal magnetization (H ⩽ 3.6 × 10⁶ A m⁻¹) for each alloy have been measured for 4 K < T < 300 K; the magnetic properties are discussed in terms of the nuclear and magnetic medium-range order as determined by small-angle neutron scattering; the measurements were done at the Institut Laue Langevin, with the D 11 spectrometer. The samples were prepared by sputtering and also, for x = 0.65, by planar flow casting. In both cases the samples are in the form of sheets 40 μm thick and 1 cm wide. For sample x = 0.65 (planar flow casting), both faces were polished with fine sandpaper along a chosen direction and then measured.