thin films of fullerite with perovskites manganites composites

O. Pană1, C.M. Teodorescu2, D. Macovei2, Al. Darabont3, N. Jumate4, R. Turcu1, M.L. Soran1

1National Institute R&D for Isotopic and Molecular Technologies,71-103 Donath Str. PO Box 700, Cluj-Napoca, Romania
2Natlional Institute R&D of Materials Physics, P.O.Box MG-7 Bucuresti-Magurele, Romania
3 “Babes-Bolyai” Univ. of Cluj, Faculty of Physics, 1 Kogalniceanu Str. Cluj-Napoca, Romania
4Technical University of Cluj-Napoca, Materials Science Department, Cluj-Napoca, Romania

The high magnetic moments in bidimensional systems, the superparamagnetism properties of metallic nanoparticles on various substrates used for obtain the magnetic field sensors, the magnetization dependence of temperature, especially low temperature, are in attention of scientifically communities. A great number of composites deposited on various substrates are based on magnetic materials with fullerenes. The advantages of fullerene (C60) are: the high stability of C60 at the high pressure (up to 20 GPa), the C60 structure is like a great spherical atom with a very great diameter and interacts strong and selective with some atom species.
In this work we performed the deposition of composites with perovskites manganites and fullerenes as thin films by co-evaporation in ultrahigh vacuum. The purity of used fullerenes was higher than 99.5% C60. The thin films were deposited on Si substrates. For film deposition, the fullerene molecules were obtained by sublimation from a Knudsen cell at 520 - 570°C, whereas the LCMO composite is evaporated by electron bombardment from a Ta crucible hit by a current 50 - 100 mA of electrons accelerated at 1.5 - 2.5 keV. The relative concentration of composite and fullerene is obtained by variation of the relative deposition rates, as measured by a quartz microbalance with typical error is less than 1%. Three sets of samples with 10%, 16% and 80% LCMO in fullerite were prepared. 
SEM and EDX methods were used for surface characterization of thin films obtained. Further, XPS investigations gives additional information on relative composition of the deposited layers, and chemical (oxidation) states of the components. Additional information concerning the compound resulted from the co-deposition process could be obtained by analyzing the IR spectra of the film. Transmission spectra were recorded in the 400 cm-1 - 800 cm-1 domain for the 10% LCMO composite film sample. This domain is restricted by the transmittance of the Si support monocrystal. For comparison various IR transmission spectra of LCMO granular manganites sintered at different temperature were also recorded.