Growth and properties of c-axis epitaxial thin films for La2-2xSr1+2xMn2O7 bilayer manganates by sputtering

c-Axis epitaxial thin films of a layered manganate La2-2xSr1+2xMn2O7 have been grown on SrTiO3(100) substrates by on-axis rf-magnetron sputtering. The films have been characterized using energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM), magnetoresistivity, and magnetization measurements. It is shown that the film chemical composition is sensitive to the deposition parameters, and that a small deviation of composition or deposition condition causes nucleation of the (La,Sr)MnO3 structure. It is found that the deposition rate is crucial for the c-axis film growth; stoichionnetric c-axis La2-2xSr1+2xMn2O7 films have been grown under limited conditions of a low rate of 0.8nm/min, an (Ar, O-2 50%) atmospheric pressure of 120mTorr, and a substrate temperature of 760 degrees C. From X-ray diffraction simulation, it is inferred that the c-axis La2-2xSr1+2xMn2O7 films thus grown contain intergrowths comprised of (La,Sr)MnO3 and presumably (La,Sr)(2)MnO4 structures, and the total intergrowth fraction amounts to about 40%.