Role of magnetic fluctuations in the luminescence line width of small systems

We discuss the magnetizations fluctuation as a leading determinant of the line width of luminescence from quantum dots composed of diluted magnetic semiconductors (DMSs) (particularly, of microluminescence from individual or small number of such quantum dots). The leading role of thermal fluctuations is related to a small volume of quantum dots—in close similarity to the case of bound magnetic polarons, the similarity is the starting point of our discussion. Our findings are fully consistent with results of recent experiments performed on CdMnSe and CdMnTe self-assembled quantum dots in several groups. The same mechanism of line broadening is also responsible for an oscillatory dependence of the luminescence line width as a function of a magnetic field observed in DMS quantum wells grown by molecular beam epitaxy using digital method of growth.