Pressure-tuned first-order phase transition and accompanying resistivity anomaly in Ce Zn1-δ Sb2

The Kondo lattice system Ce Zn0.66 Sb2 is studied by electrical resistivity and ac magnetic susceptibility measurements at several pressures. At P=0 kbar, ferromagnetic and antiferromagnetic transitions appear at 3.6 and 0.8 K, respectively. The electrical resistivity at TN dramatically changes from the Fisher-Langer type (ferromagneticlike) to the Suezaki-Mori (SM) type near 17 kbar, i.e., from a positive divergence to a negative divergence in the temperature derivative of the resistivity. The pressure-induced SM-type anomaly, which shows thermal hysteresis, is easily suppressed by a small magnetic field (1.9 kOe for 19.8 kbar), indicating a weakly first-order nature of the transition. By subtracting a low-pressure data set, we directly compare the resistivity anomaly with the SM theory without any assumption on backgrounds, where the negative divergence in dρ dT is ascribed to enhanced critical fluctuations in the presence of superzone gaps. © 2005 The American Physical Society