Photo-induced magnetization rotation in III–V ferromagnetic alloy semiconductor quantum wells

We have prepared a series of single quantum wells consisting of a (Ga,Mn)As well and have studied the photo-induced magnetization rotation by means of the time-resolved Kerr rotation measurements with circularly polarized light. In the magnetic circular dichroism spectra, the characteristic broad structure around the band gap energy shifts towards to higher energies with decreasing well layer thickness, indicating the formation of quantized states in a magnetic well. Temporal profile of polar Kerr rotation for the 5-nm quantum wells (QW) (View the MathML source) reveals magnetization rotation from in-plane to out-of-plane direction without the external magnetic fields, with the magnitude of rotation being about 40 times larger than that reported in the bulk. The observed enhancement is discussed in terms of enhanced polarization of hole spins which results from non-degenerate light and heavy hole bands in the QWs.