  We have investigated the magnetic and chemical properties of very thin Cr
films, CrAs, and arsenized Cr grown by molecular beam epitaxy on Ga As (001),
using x-ray photoemission spectroscopy and SQUID magnetometry. Distintic
preparation procedures have been used with the purpose to undestand the origin
of the ferromagneti signal observed for this system. It results that Ga
segregation and chemical reactivity between Ga and Cr have negligible
contribution in the formation of different thi films. A clear ferromagnetic
response even at room temperature suggests the existence of a very thin
interfacial layer formed that can eventually be burid during the growth
process.
