Large spin polarization in Ga$_{1-x}$Mn$_{x}$P synthesized by ion implantation and pulsed-laser melting

We have recently demonstrated that the mediating holes in Ga$_{1-x}$Mn$_{x}$P reside in an impurity band separated from the valence band by a gap [Scarpulla \textit{et al.}, Phys. Rev. Lett. \textbf{95} 207204 (2005)]. For samples with x$\approx $0.06 and Curie temperature 60 K, this gap is approximately 25 meV. In this work, we demonstrate a very large spin polarization of states near the Fermi level across a range of Mn compositions using Mn L$_{3,2}$ X-ray magnetic circular dichroism (XMCD). We find that the X-ray absorption spectrum at the Mn L$_{3,2}$ edge is very similar to that observed in Ga$_{1-x}$Mn$_{x}$As [Edmonds \textit{et al.}, Appl. Phys. Lett. \textbf{84} 4065 (2004)], indicating that the Mn bonding environment is similar between Ga$_{1-x}$Mn$_{x}$As and Ga$_{1-x}$Mn$_{x}$P. The magnitude of the X-ray fluorescence XMCD signal reaches approximately 70{\%} at the Mn L$_{3}$ edge across the range of compositions, indicating a large spin asymmetry in the density of states. This is consistent with (but not exclusive to) the existence of a spin-polarized impurity band near the Fermi level.