Structural and magnetic properties of U(Co, T)Al solid solutions (T = Ru, Rh, Pt)

Complete text of publication follows. UTA1 compounds (T = transition metal) with the hexagonal ZrNiAl-type structure exhibit a variety of magnetic ground states from Pauli paramagnetism to ordering of U magnetic moments. UCoAl is a 5f-band metamagnet. URuAl, URhAl and UPtAl have paramagnetic, ferromagnetic and antiferromagnetic ground states, respectively. Magnetic properties of these compounds can be altered in solid solutions, which cause a change in 5f-ligand hybridization which affects both the formation of U magnetic moments and the exchange coupling between them. Neutron-diffraction studies of U(Co, T)Al solid solutions are presented where 2/3 of the Co atoms are substituted by Ru, Rh or Pt. Two types of information were obtained: a) crystal structure, occupation of the Co1 and Co2 positions by substituting atoms, e.g. all Ru atoms reside on Co2 positions, whereas pure statistical distribution is found for Rh substitutions, and b) magnetic ordering, long-range magnetic order of reduced U moments was confirmed for all three compounds. Correlation between the crystal and magnetic structure is discussed in terms of 5f-ligand hybridization effects. (author)