Infrared conductivity of metallic (III,Mn)V ferromagnets

摘要

We present a theory of the infrared conductivity and absorption coefficientsof metallic (III,Mn)V ferromagnetic semiconductors. We find that theconductivity is dominated by inter-valence-band transitions that produce peaksat $\hbar \omega \sim 220 {\rm meV}$ and obscure the broadened Drude peak. Wedemonstrate that transverse f-sum rule measurements can be used to extractaccurate values for the free carrier density, bypassing the severecharacterization difficulties that have till now been created by the largeanomalous Hall effect in these materials.