Neutron diffraction studies of the magnetic ordering in the rare earth compounds TbNi2Si2, HoCo2Si2 and TbCo2Si2

Neutron diffraction studies and magnetic measurements on the compounds TbNi₂Si₂ (1), HoCo₂Si₂ (2) and TbCo₂Si₂ (3) revealed a collinear antiferromagnetic order below T_N = 10 ± 1 K (1), T_N = 13 ± 1 K (2) and T_N = 30 ± 2 K (3) with the rare earths moments oriented along the c-axis m₀ = 8.8 ± 0.2 μ_B (1), m₀ = 8.1 ± 0.2 μ_B (2), m₀ = 8.8 ± 0.2 μ_B (3)] and the corresponding wavevector are $\text{k}\text{=}\text{1}\text{2}\text{1}\text{2}\text{0] (1)}\text{and}\text{k}\text{= 0 0 1] (2) (3)}$. The magnetic structure of the compounds HoCo₂Si₂ and TbCo₂Si₂ consists of ferromagnetic layers perpendicular to the c-axis coupled antiferromagnetically (+?+?) while for TbNi₂Si₂ the ordering within (0 0 1) plane is antiferromagnetic and the planes (0 0 1) are indeed decoupled.