Abstract
The scene is set by a discussion of magnetism in pristine ZnO and ZnCoO which does not contain nanoparticles.  Doping with aluminium at low concentrations is shown to be beneficial. This is followed by a description of the behaviour of an array of nanoparticles including the situation where they are very small.  A number of experiments are described that have been done on composite ZnO/Co materials which demonstrate the polarisation of mobile carriers as well as Co nanoparticles.  Finally a series of experiments that demonstrate the coupling, which is actually dependent on the addition of aluminium, will be discussed.