Low temperature magnetic response of CePt surface alloy

We have used X-ray magnetic circular dichroism (XMCD) at Cerium edges to determine the low temperature paramagnetic local moment response of a CePt intermetallic surface alloy. The ultrathin alloy film is prepared in situ by evaporation of few atomic layers of Ce onto Pt(111) and subsequent annealing. LEED patterns of the resulting alloy hint at a (1.85 x 1.85) superstructure. The temperature dependent susceptibility is partially compatible with the response of the crystal field split Ce 4f1 state with a crystal field splitting of ∼60 K. Below 20 K our data are indicative of a magnetic phase transition at a critical temperature of ∼9 K. We discuss our results in view of the recent findings of Kondo lattice physics in the related CePt5 surface alloy.