Thickness dependence of magneto-optical effects in (Ga,Mn)As epitaxial layers

Rotation angle (theta(MO)) of a linearly polarized light reflected from in-plane, ferromagnetic (Ga,Mn)As layers was measured precisely using a magneto-optical microscope. The theta(MO) value varies non-linearly as a function of (Ga,Mn)As layer thickness d, showing a maximum at d = 50-60 nm. The thickness dependent theta(MO) was analyzed quantitatively with a model based on an interference effect incorporating birefringence and dichroism, and it has been concluded that the contribution of magnetization-vector dependent refractive index, a magnetic birefringence, is responsible for the observed magneto-optical effect. The magnitude of magnetic birefringence appears to be comparable to those of uniaxial birefringence crystals. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4724215]