Density dependence of zinc-blende MnAs dots studied by X-ray absorption spectroscopy and X-ray magnetic circular dichroism

Zinc-blende type nanoscale MnAs dots were grown on a sulfur-passivated GaAs (0 0 1) surface by molecular beam epitaxy. We report on the dot density dependence of the X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) in the Mn 2p core-level region. The XAS spectrum of low-density MnAs dots showed 'localized' behavior as in the case of (Ga,Mn)As, while the spectrum of high-density MnAs dots changed to metallic behavior. The magnetic-field dependence of the XMCD revealed ferromagnetic behavior in the case of high-density MnAs dots