The conductivity and magnetization of Fe1-xCoxS2 were measured to investigate quantum critical behavior in disordered itinerant magnets. Small x (<0.001) is required to convert insulating iron pyrite into a metal, followed by a paramagnetic-to-ferromagnetic metal transition at x = 0.032+/-0.004. Singular contributions are discovered that are distinct from those at either metal-insulator or magnetic transitions. Our data reveal that disorder and low carrier density associated with proximity to a metal-insulator transition fundamentally modifies the critical behavior of the magnetic transition.
@article{arxiv.cond-mat/0306541,
title = {The Effect of Disorder on a Quantum Phase Transition},
author = {J. F. DiTusa and S. Guo and D. P. Young and R. T. Macaluso and D. A. Browne and N. L. Henderson and J. Y. Chan},
journal= {arXiv preprint arXiv:cond-mat/0306541},
year = {2007}
}