Yb2(Pd1-xNix)2Sn: Interplay of Geometrical Frustration and Kondo Effect in Quantum Spin System

Abstract

Single crystals of Yb 2 (Pd 1- x Ni x ) 2 Sn with x =0, 0.1, and 0.2 were prepared to clarify the effects of pressure on Yb 2 Pd 2 Sn which is considered to reside near the quantum critical point. The magnetization and specific heat measurements revealed that their ground states are regarded as an S =1/2 XY-like spin system. Although nondoped Yb 2 Pd 2 Sn shows no magnetic transition down to 0.5 K owing to the Kondo effect, Ni-doped Yb 2 Pd 2 Sn exhibits a distinct magnetic transition. Furthermore, the magnetic susceptibility of Ni-doped Yb 2 Pd 2 Sn exhibits a broad peak in the temperature range higher than the magnetic transition temperature, which is not explained by the S =1/2 Coqblin–Schrieffer model, suggesting the effect of geometrical frustration arising from the characteristic structure of these compounds, i.e., the Shastry–Sutherland lattice.