Neutron scattering studies on Yb$_{3}$Pt$_{4}$

The antiferromagnetic (AF) intermetallic compound Yb$_{3}$Pt$_{4}$ shows a magnetic phase diagram which includes a quantum critical point, but is different from other Yb-containing quantum critical compounds. We elucidated the zero-field behavior by neutron scattering on both polycrystal and single-crystal samples. The magnetic structure due to the single-site-low-symmetry Yb moments was determined by diffraction. The AF unit cell coincides with the crystallographic unit cell, and shows pairs of Yb nearest-neighbor moments pointing directly towards each other. The order parameter is consistent with a continuous transition at the N\'{e}el temperature (2.4 K) and can be described by a simple mean-field model. The ordered moment amounts to $\sim $ 1.2 $\mu _{B}$/Yb at 0 K. Inelastic neutron scattering reveals that the crystal electric field lifts the degeneracy of the Yb 4f ground state into 4 doublets, consistent with specific heat results.