  The recent study of oxides led to the discovery of several new fascinating
physical phenomena. High-temperature superconductivity, colossal
magnetoresistance, dilute magnetic doping, or multiferroicity were discovered
and investigated in transition-metal oxides, representing a prototype class of
strongly correlated electronic systems. This development was accompanied by an
enormous progress regarding thin film fabrication. Within the past two decades,
epitaxial thin films with crystalline quality approaching semiconductor
standards became available using laser molecular beam epitaxy. This evolution
is reviewed, particularly with emphasis on transition-metal oxide thin films,
their versatile physical properties, and their impact on the field of
spintronics. First, the physics of ferromagnetic half-metallic oxides, such as
the doped manganites, the double perovskites and magnetite is presented
together with possible applications based on magnetic tunnel junctions. Second,
the wide bandgap semiconductor zinc oxide is discussed particularly with regard
to the controversy of dilute magnetic doping with transition-metal ions and the
possibility of realizing p-type conductivity. Third, the field of oxide
multiferroics is presented with the recent developments in single-phase
multiferroic thin film perovskites as well as in composite multiferroic
hybrids.
