Neutron diffraction measurements were carried out on single crystals and powders of ${\mathrm{Yb}}_2{\mathrm{Pt}}_2\mathrm{Pb}$, where Yb moments form two interpenetrating planar sublattices of orthogonal dimers, a geometry known as Shastry-Sutherland lattice, and are stacked along the $c$ axis in a ladder geometry. ${\mathrm{Yb}}_2{\mathrm{Pt}}_2\mathrm{Pb}$ orders antiferromagnetically at $T_N=2.07\mathrm{K}$, and the magnetic structure determined from these measurements features the interleaving of two orthogonal sublattices into a $5\times 5\times 1$ magnetic supercell that is based on stripes with moments perpendicular to the dimer bonds, which are along $\left(110\right)$ and $(-110)$. Magnetic fields applied along $\left(110\right)$ or $(-110)$ suppress the antiferromagnetic peaks from an individual sublattice, but leave the orthogonal sublattice unaffected, evidence for the Ising character of the Yb moments in ${\mathrm{Yb}}_2{\mathrm{Pt}}_2\mathrm{Pb}$ that is supported by point charge calculations. Specific heat, magnetic susceptibility, and electrical resistivity measurements concur with neutron elastic scattering results that the longitudinal critical fluctuations are gapped with $\mathrm{\Delta }E\simeq 0.07\mathrm{meV}$.

• Received 8 July 2014
• Revised 12 December 2015

DOI:https://doi.org/10.1103/PhysRevB.93.104419