EuPd$_{3}$ ultrathin layers on MgO(001)*

Ultrathin layers (0.8 -- 4 nm thick) of EuPd$_{3}$ intermetallic compound were grown on MgO(001) substrates by molecular beam epitaxy from elemental sources. In-situ X-ray photoelectron spectroscopy studies revealed a dominant trivalent europium component, in agreement with available data on bulk EuPd$_{3}$ (e.g. [1, 2]). As demonstrated by reflection high energy electron diffraction and X-ray photoelectron spectroscopy, growth by co-deposition at elevated temperature ($\sim $500 \r{ }C) or post-growth annealing of Pd/Eu/Pd layers resulted in formation of islands. Formation of EuPd$_{3}$ occurs at lower temperatures. Trivalent europium at Pd layers interface was observed even at room temperature. 250 \r{ }C is sufficient to form EuPd$_{3}$ from individual Pd and Eu layers. [1] I.R. Harris, G.V. Raynor, J. Less-Common Met. \textbf{9}, 263 (1965). [2] W.-D. Schneider, C. Laubschat, I. Nowik, G. Kaindl, Phys. Rev. B, Condens. Matter \textbf{24}, 5422 (1981).