Yb2Pt2Pb: Magnetic frustration in the Shastry-Sutherland lattice

Abstract

We have synthesized single crystals of ${\text{Yb}}_{2}{\text{Pt}}_{2}\text{Pb}$, which crystallize in the layered ${\text{U}}_{2}{\text{Pt}}_{2}\text{Sn}$-type structure, where planes of Yb ions lie on a triangular network. Here, we report the results of magnetization, specific heat, and electrical resistivity experiments. The lattice constants and high temperature magnetic susceptibility indicate that the Yb ions are trivalent, while the Schottky peaks in the specific heat show that the ground state is a well isolated doublet. A significant magnetic anisotropy is observed, with the ratio of susceptibilities perpendicular and parallel to the magnetic planes differing by as much as a factor of 30 at the lowest temperatures. Antiferromagnetic order occurs at a N\'eel temperature ${T}_{N}=2.07\text{ }\text{K}$. Evidence of short range magnetic fluctuations is found in the magnetic susceptibility and electrical resistivity, which have broad peaks above ${T}_{N}$, and in the slow development of the magnetic entropy at ${T}_{N}$. Our experiments indicate that ${\text{Yb}}_{2}{\text{Pt}}_{2}\text{Pb}$ is a quasi-two-dimensional and localized moment system, where strong magnetic frustration may arise from the geometry of the underlying Shastry-Sutherland lattice.