Magnetic correlations in the intermetallic antiferromagnet Nd₃Co₄Sn₁₃

Specific heat, magnetic susceptibility, and neutron scattering have been used to investigate the nature of the spin system in the antiferromagnet Nd₃Co₄Sn₁₃. At room temperature Nd₃Co₄Sn₁₃ has a cubic, Pm-3n structure similar to Yb₃Rh₄Sn₁₃. Antiferromagnetic interactions between, Nd³⁺ ions dominate the magnetic character of this sample and at 2.4 K the Nd spins enter a long range order state with a magnetic propagation vector q  =  (0 0 0) with an ordered moment of 1.78(2) µ_B at 1.5 K. The magnetic Bragg intensity grows very slowly below 1 K, reaching ~2.4 µ_B at 350 mK. The average magnetic Nd³⁺ configuration corresponds to the 3D irreducible representation Γ₇. This magnetic structure can be viewed as three sublattices of antiferromagnetic spin chains coupled with each other in the 120°-configuration. A well-defined magnetic excitation was measured around the 1 1 1 zone centre and the resulting dispersion curve is appropriate for an antiferromagnet with a gap of 0.20(1) meV.