Fluctuation-induced non-Fermi-liquid behavior near a quantum phase transition in itinerant electron systems

The signature for a non-Fermi-liquid behavior near a quantum phase transition has been observed in thermal and transport properties of many metallic systems at low temperatures. In the present work we consider specific examples of an itinerant ferromagnet as well as an antiferromagnet in the limit of vanishing transition temperature. The temperature variation of spin susceptibility, electrical resistivity, specific heat, and NMR relaxation rates at low temperatures is calculated in the limit of infinite exchange enhancement within the framework of a self-consistent spin fluctuation theory. The resulting non-Fermi-liquid behavior is due to the presence of the low-lying critically damped spin fluctuations in these systems. The theory presented here gives the leading low-temperature behavior, as it turns out that the fluctuation correlation term is always smaller than the mean fluctuation field term in three as well as in two space dimensions. A comparison with illustrative experimental results of these properties in some typical systems has been done. Finally, we make some remarks on the effect of disorder in these systems.