Unconventional resistivity at the border of metallic antiferromagnetism in NiS$_2$
P. G. Niklowitz, P. L. Alireza, M. J. Steiner, G. G. Lonzarich, D. Braithwaite, G. Knebel, J. Flouquet, and J. A. Wilson

We report low-temperature and high-pressure measurements of the electrical resistivity $\rho(T)$ of the antiferromagnetic compound NiS$_2$ in its high-pressure metallic state. The form of $\rho(T,p)$ suggests the presence of a quantum phase transition at a critical pressure $p_c=76\pm 5$~kbar. Near $p_c$ the temperature variation of $\rho(T)$ is similar to that observed in NiS$_{2-x}$Se$_x$ near the critical composition $x=1$ where metallic antiferromagnetism is suppressed at ambient pressure. In both cases $\rho(T)$ varies approximately as $T^{1.5}$ over a wide range below 100~K. This lets us assume that the high-pressure metallic phase of stoichiometric NiS$_2$ also develops itinerant antiferromagnetism, which becomes suppressed at $p_c$. However, on closer analysis the resistivity exponent in NiS$_2$ exhibits an undulating variation with temperature not seen in NiSSe ($x=1$). This difference in behaviour may be due to the effects of spin-fluctuation scattering of charge carriers on cold and hot spots of the Fermi surface in the presence of quenched disorder, which is higher in NiSSe than in stoichiometric NiS$_2$.

© 2008 The American Physical Society.