Abstract
Measurements of magnetic properties, X-ray and neutron diffraction, differential thermal analysis (DTA), thermal expansion and resistivity were made on Gd(Fe1-xAlx)2 and Dy(Fe1-xAlx)2. Both systems exhibit a line broadening observed by X-ray diffraction on the Al-rich side, indicating a small variation of the lattice constants. This effect leads to a smoothing of the magnetic phase transition at the Curie temperature Tc, which becomes observable in all the measurements mentioned above. The neutron experiments give evidence of a disordered component of the Dy moment due to Fe substitution. By subtracting the thermal expansion of non-magnetic YAl2 from that of the mixed crystal series, a reduction of the spontaneous magnetostriction from its value in the corresponding boundary phase is also obtained. In the case of anisotropic Dy the magnetisation behaviour can be explained by the pinning of narrow domain walls on inhomogeneities caused by chemical substitution. All physical properties indicate a magnetically quasi-amorphous state.