We have studied Mn/InAs(0 0 1)(4 x 2)c(8 x 2) interfaces by high-resolution core-level spectroscopy, surface EXAFS and by X-ray magnetic circular dichroism (XMCD). The growth of manganese is found to depend strongly on the temperature of InAs. At low temperatures (room and liquid nitrogen temperature (LNT)), Mn atoms form the compound MnAs in the surface region leaving metallic In islands on the surface. Manganese deposition at 530 K results in strong diffusion of Mn into the substrate followed by formation of the compound In1-xMnAs in which Mn atoms are substituted in indium-sites. We show by XMCD that In1-xMnxAs is ferromagnetic with a relatively high value of an average magnetic moment per Mn atom, exceeding 0.7 muB at low temperatures and with an individual magnetic moment of about 2.4 muB. The temperature dependence of the Mn magnetic moment follows the Brillouin function and it drops to zero at temperature of about 150 K for measurements in an external magnetic field of 5 T. (C) 2003 Published by Elsevier Science B.V.