ATOMICALLY DEFINED EPITAXY AND PHYSICAL-PROPERTIES OF STRAINED LA0.6SR0.4MNO3 FILMS

La0.6Sr0.4MnO3 thin films were fabricated on SrTiO3 (001) substrates u sing pulsed laser deposition with observing persistent intensity oscil lation of reflection high- energy electron diffraction. By atomic forc e microscopy, the surface of resulting films was confirmed to be extre mely flat, showing atomically smooth terraces and 0.4 nm high steps co rresponding to a unit cell height of perovskite. The surface terminati ng atomic layer was unambiguously assigned to the MnO2 layer by coaxia l impact collision ion scattering spectroscopy. Crystal symmetry of th e films is distorted into a tetragonal one due to the strain to fulfil l perfect in-plane matching with the substrate even for films as thick as 100 nm. Even for films as thin as 4 nm (10 unit cells), ferromagne tic transition takes place to induce a metallic state and large negati ve magnetoresistance is observed as well. (C) 1998 American Institute of Physics. [S0003-6951(98)02343-2].