A comparison of the structural and magnetic properties of FePt nanostructures grown at different temperatures on NaCl (001) and MgO (001) substrates is presented. A strong influence of the deposition temperature on the epitaxial growth as well as on the size distribution of FePt nanostructures grown on NaCl substrates is observed. In spite of a large lattice mismatch between FePt and NaCl, a'cube-over-cube'growth of nanostructures with a narrow size distribution was achieved at 520 K. Moreover, the growth of FePt nanostructures on NaCl (001) is not preceded by the formation of a wetting layer as observed on MgO (001). The higher degree of L1 0 chemical ordering in FePt nanostructures grown on MgO (001) accompanied by the absence of L1 0 variants with an in-plane tetragonal c-axis indicates that the tensile epitaxial stress induced by the MgO substrate is a key factor in the formation of the L1 0 phase with …