We have tried to clarify the magnetic property of a c(2×2) CuMn two-dimensional ordered surface alloy, which has been probed by Mn L23 X-ray magnetic circular dichroism (XMCD) spectra using a helicity modulation technique for the incident circularly polarized synchrotron radiation at BL 25 SU of SPring-8. In this work, a local magnetic susceptibility has been firstly applied to this surface alloy system, which has been deduced from the temperature dependence of the XMCD spectra. It is found that the local magnetic susceptibility above 40 K obeys the Curie-Weiss law. The evaluated positive value of the Weiss temperature Θ = 20 K clearly suggests the ferromagnetic interaction between the Mn atoms, although the expected Curie temperature is much reduced compared to the predicted value.
