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

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Single crystals of Yb2(Pd1-xNix)2Sn with $x=0$, 0.1, and 0.2 were prepared to clarify the effects of pressure on Yb2Pd2Sn 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 Yb2Pd2Sn shows no magnetic transition down to 0.5 K owing to the Kondo effect, Ni-doped Yb2Pd2Sn exhibits a distinct magnetic transition. Furthermore, the magnetic susceptibility of Ni-doped Yb2Pd2Sn 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.
2009-08-15