With the development of techniques for producing materials not found in nature, a number of new and exciting phenomena have become available for study in the field of condensed matter physics. Many of these phenomena are based on magnetism, in particular the joining of magnetic materials with those which are nonmagnetic. We study the behavior of heterogeneous condensed systems in which a magnetic component plays a crucial role. In essence, magnetism is introduced as a new degree of freedom to manipulate and to probe dynamics. Our emphasis at this time is on two very different kinds of systems: metal-semiconductor (MS) contacts in which the metal is ferromagnetic, and liquid suspensions of small (~1 micron) particles containing a magnetic core. In the case of the MS structures, we are interested in the dynamical behavior of electrons, while in the suspensions particle dynamics is the focus.

Probing dynamics via magnetism is accomplished using a number of tools, including magnetrotransport, inelastic electron tunneling spectroscopy, electron spin resonance and radio frequency permeability measurements. We are particularly interested in developing new techniques based on nuclear magnetic resonance (NMR), and have recently purchased a state-of-the-art NMR spectrometer. In MS structures, the injection of spin-polarized electrons from a ferromagnetic electrode to a semiconductor will result in dynamical polarization of nuclei as the latter interact with the polarized electrons. These effects can be used to study the distribution of nonequilibrium electron spin polarization in the semiconductor. The rotational dynamics of suspended magnetic particles is accessible with the methods of two-dimensional NMR. This is based on the dependence of the nuclear resonance on orientation with respect to an external field, and the consequent evolution of nuclear magnetization with particle rotation.