Magnetic properties of UT2Si2 and UT2Ge2 (T = Co,Ni, Cu) intermetallic systems

Neutron diffraction and magnetization measurements indicate that, at low temperatures, long-range magnetic order is present in UCO₂Si₂, UNi₂Si₂, UCu₂Si₂, UNi₂Ge₂, and UCo₂Ge₂. UCo₂Si₂ and UNi₂Ge₂ are simple collinear antiferromagnets of +-+- type, UCu₂Si₂ a simple collinear ferromagnet. In UNi₂Si₂, a magnetic phase transition from a LSW type structure to collinear antiferromagnetism of +-+- type was found, while in UCu₂Ge₂, the antiferromagnetic structure of ++-- transforms into collinear ferromagnetism. Crystal structure and magnetic parameters are given. No magnetic moment on transition metal ions was found within the accuracy of a powder neutron diffraction experiment. The stability of particular magnetic ordering schemes is discussed in terms of an isotropic RKKY mechanism.