Novel phases near magnetic quantum phase transitions

Hilbert v. Löhneysen (Physikalisches Institut, Universität Karlsruhe, D-7128 Karlsruhe, Germany and Forschungszentrum Karlsruhe, Institut für Festkörperphysik, D-76021 Karlsruhe, Germany)

In an number of magnetic systems, the magnetic ordering temperature Tc can be tuned to absolute zero by an external parameter such as pressure, composition, or magnetic field. Such a quantum phase transition manifests itself through unusual thermodynamic and transport properties. In addition, the tuning of Tc to zero offers the possibility that low energy scales, otherwise masked by the magnetic interactions, become important, leading to novel magnetic phases. The unusual behavior near quantum critical transitions will be illustrated by two examples,the heavy-fermion compound CeCu6-xAux and the weak itinerant ferromagnet MnSi.