Magnetic phase diagrams of UCu₂Si₂ and UNi ₂Si₂

Magnetization measurements performed on UCu2Si2 and UNi2Si2 are reported. The compound UCu2Si 2 appears to undergo both an antiferromagnetic (AFM) transition at T≊107 K and a ferromagnetic (FM) transition at Tc≊103 K. While the second transition at Tc has already been reported, the AFM phase was apparently overlooked in earlier studies. The compound UNi 2Si2 undergoes a transition at T≊97 K, which was previously shown to be AFM by neutron scattering; we present evidence for the occurrence of a FM state below the AFM transition.