MAGNETIC-ANOMALIES IN DISORDERED ELECTRONIC SYSTEMS

We review some recent results in the theory of disordered electrons. We find that the metal-insulator transition is preceded on the metallic side by a phase transition leading from diffusive to subdiffusive spin transport. This new phase transition is characterized by a vanishing spin diffusion constant, a diverging spin susceptibility, a logarithmic anomaly in the specific heat, and an uncritical electrical conductivity. In the vicinity of this phase transition, perturbation theory simplifies substantially. This allows for an infinite resummation of the loop expansion, and for an exact evaluation of the critical exponents. The phase transition can be obtained both by a renormalization group analysis, and by solving the integral equations which result from the infinite resummation. The results are in good agreement with experiments on Si:P. © 1990.