Hydrostatic pressure study of pure and doped La_1−xR_xAgSb₂ (R=Ce,Nd) charge-density-wave compounds

The intermetallic compound LaAgSb₂ displays two charge-density-wave (CDW) transitions, which were detected with measurements of electrical resistivity (ρ), magnetic susceptibility, and x-ray scattering; the upper transition takes place at T₁≈210 K, and it is accompanied by a large anomaly in ρ(T), whereas the lower transition is marked by a much more subtle anomaly at T₂≈185 K. We studied the effect of hydrostatic pressure (P) on the formation of the upper CDW state in pure and doped La_1−xR_xAgSb₂ (R=Ce,Nd) compounds by means of measurements of ρ(T) for P⩽23 kbar. We found that the hydrostatic pressure, as well as the chemical pressure introduced by the partial substitution of the smaller Ce and Nd ions for La, results in the suppression of the CDW ground state—e.g., the reduction of the ordering temperature T₁. The values of dT₁∕dP are ≈2–4 times higher for the Ce-doped samples as compared to pure LaAgSb₂, or even La_0.75Nd_0.25AgSb₂ with a comparable T₁ (P=0). This increased sensitivity to pressure may be due to increasing Ce hybridization under pressure. The magnetic-ordering temperature of the cerium-doped compounds is also reduced by pressure, and the high-pressure behavior of the Ce-doped samples is dominated by Kondo impurity scattering.