Crystallographic and magnetic properties of UFe5.8Al6.2 single crystals

Single crystals of UFe5.8Al6.2 were characterised by X-ray and neutron diffraction, Fe-57 Mossbauer spectroscopy and magnetisation. The structure refinement by X-ray and neutron diffraction shows a ThMn12-type structure, the Fe atoms fully occupying the 8f and partially occupying the 8j positions. Mossbauer spectra confirm these occupations and further indicate a magnetic ordering below 293 K. Magnetisation measurements show a ferromagnetic behaviour below 300 K, with a and b as easy directions and a spontaneous magnetisation of 10.4 mu(B)/f.u. at 5 K, due to the Fe occupation of 8j position. These single crystal results significantly differ from those previously obtained in UFe6Al6 polycrystalline samples obtained by melting and annealing.