Effect of temperature on hybridization and magnetism in U ₂Pd₂Sn and U₂Ni₂In

We report on the temperature variation of the interatomic distances in isostructural U₂Ni₂In and U₂Pd₂Sn, both of which order antiferromagnetically at low temperatures. Both compounds exhibit complex non-collinear arrangements of the magnetic moments confined to the tetragonal basal plane, which is perpendicular to the shortest interuranium distance along the c-axis at low temperatures. The different temperature dependencies of the shortest interatomic links between uranium and the transition metal (Ni or Pd) provide evidence for the dual nature of 5f-d hybridization in these two compounds. We argue that magnetic ordering in U ₂Pd₂Sn arises due to increased 5f-d hybridization (promoting stronger exchange) while the reduced hybridization in U ₂Ni₂In allows for the formation of stable U magnetic moments.