Single-crystalline samples of ${\mathrm{YbInCu}}_4$ and its partially substituted compounds by Y and Lu were synthesized by the flux method. The temperature dependence of the magnetic susceptibility from 2 to 320 K in the magnetic field of 0.5 T and the high-field magnetization up to 41 T under various fixed pressures were measured in order to investigate the effect of substitution, inherent chemical pressure, and external pressure on the first-order valence transition of ${\mathrm{YbInCu}}_4.$ Substitution of Yb by Y or Lu results in a small increase or decrease of the lattice parameter, while both systems show a steep decrease of transition temperature ${(T}_v)$ and transition magnetic field ${(H}_v)$ with substitution, resulting in suppression of the valence transition around $x=0.30\mathrm{}$ for ${\mathrm{Yb}}_{1-x}{\mathrm{Y}}_x{\mathrm{InCu}}_4\hspace{0.5em}(0\mathrm{}<~x<~0.3)$ and $x=0.15\mathrm{}$ for ${\mathrm{Yb}}_{1-x}{\mathrm{Lu}}_x{\mathrm{InCu}}_4\hspace{0.5em}(0\mathrm{}<~x<~0.15).$ The effect of pressure on $H_v$ of the pure and Y-substituted ${\mathrm{YbInCu}}_4$ is reported by ${\mathrm{dH}}_v/dP\approx -1\hspace{0.5em}\mathrm{T}/\mathrm{k}\mathrm{b}\mathrm{a}\mathrm{r},$ with a suppression of the valence transition of ${\mathrm{Yb}}_{0.8}{\mathrm{Y}}_{0.2}{\mathrm{InCu}}_4$ at the pressure of 8 kbar. The effect of inherent chemical pressure is very small compared with the intrinsic effect of substitution. The decreasing of Kondo temperature $T_K(\propto 1/{\chi }_0)$ below $T_v$ resulting from the substitution for the Yb lattice is discussed as an important factor affecting the valence transition of ${\mathrm{YbInCu}}_4.$

• Received 12 July 2001

DOI:https://doi.org/10.1103/PhysRevB.66.024112