Abstract
Single crystals of have been investigated by means of specific heat measurements at zero pressure and electrical resistivity measurements under nearly hydrostatic pressure up to . Specific heat measurements for samples of with cobalt concentrations of , 0.71, 0.77, 0.87, and 0.93 confirm the existence of antiferromagnetism for and suggest the existence of a quantum critical point at . Entropy versus isotherms below and the normalized residual resistivity versus curve both display maxima near , suggesting further evidence for the existence and location of the quantum critical point. Electrical resistivity measurements under pressure for samples with , 0.2, 0.4, and 0.6 reveal antiferromagnetism, pressure-induced superconductivity, and the coexistence of antiferromagnetism and superconductivity. Normalized residual resistivity versus pressure curves and the evolution of the power-law exponent favor the existence of quantum critical points at critical pressures , , and for samples with , 0.2, and 0.4, respectively.
4 More- Received 25 January 2005
DOI:https://doi.org/10.1103/PhysRevB.72.024551
©2005 American Physical Society