This paper reviews the present understanding of the origin of ferromagnetic response that has been detected in a number of diluted magnetic semiconductors (DMS) and diluted magnetic oxides (DMO) as well as in some nominally magnetically undoped materials. It is argued that these systems can be grouped into four classes. To the first belong composite materials in which precipitations of a known ...

We review the first decade of extensive optical studies of ferromagnetic, III-Mn-V diluted magnetic semiconductors. Mn introduces holes and local moments to the III–V host, which can result in carrier mediated ferromagnetism in these disordered semiconductors. Spectroscopic experiments provide direct access to the strength and nature of the exchange between holes and local moments; the degree o...