What has been measured by reflection magnetic circular dichroism in Ga_1–xMn_xAs/GaAs structures?

An explicit expression of reflection magnetic circular dichroism (R_MCD) has been derived, taking into account the interference effect that arises from multiple internal reflections in an air/Ga_1–xMn_xAs/GaAs dielectric layered system. It unambiguously shows that the R_MCD signal is composed by three terms. In addition to the conventional term, which is sufficient in the absence of interference, an oscillatory term is required. Both of them are related to the imaginary part ε″_xy of the off-diagonal element of the dielectric tensor. One also becomes aware that in this case R_MCD is not actually determined only by the imaginary part ε″_xy of the off-diagonal element of the dielectric tensor, as has been widely accepted. In fact, the real part ε'_xy of the off-diagonal element will substantially mix into the measured R_MCD results by another oscillatory cos θ form. It can even reverse the sign of R_MCD, when the Ga_1–xMn_xAs layer becomes thicker. The main aspects of these predictions were used to reasonably explain the R_MCD results measured in three different types of samples. Our work will bring about a reconsideration of how to correctly explain R_MCD results. (condensed matter: electronic structure, electrical, magnetic, and optical properties)