Sublattice contributions to the magnetism of UFe5Al7 and UFe6Al6

Magnetization study of intermetallic compounds UFe5Al7 and UFe6Al6 with the ThMn12-type tetragonal crystal structure is performed on single crystals. The compounds are ferromagnets with Curie temperatures of 275 K and 315 K, respectively, and possess large magnetocrystalline anisotropy of the easy-plane type with the anisotropy field exceeding 20 T. It is contributed from the U sublattice, because the Fe sublattice provides the anisotropy by an order weaker. In both UFe5Al7 and UFe6Al6, a noticeable anisotropy within the basal plane is observed with the [110] axis as the easy-magnetization direction, the [100] curve saturates in fields above 1 T. The in-plane anisotropy is a next evidence for the U magnetism because it was not observed in Lu analogue. The large anisotropy persists in the paramagnetic state as well, again due to the U sublattice because it is absent in LuFe6Al6. Magnetic moments of the U and Fe atoms are estimated as 1.8μB and 1.3μB, respectively.