Phase separation and disorder in half metallic ferromagnetic manganite thin films: A theoretical study looking forward low noise nano-devices S. Mercone a, * , L. Me ´chin a , C.A. Perroni b , J.M. Routoure a , U. Scotti di Uccio c , L. Maritato d , V. Cataudella e a GREYC (UMR 6072), ENSICAEN & University of Caen, 6 Bd. Mare ´chal Juin, 14050 Caen cedex, France b IFF, Forschungszentrum Ju ¨ lich, 52425 Julich, Germany c Coherentia-INFM and Di.M.S.A.T, Universita ` di Cassino, Italy d Coherentia-INFM and Dipartimento di Fisica ‘‘E. R. Caianiello’’, Universita ` di Salerno, Via S. Allende, 84081 Baronissi (SA), Italy e Coherentia-INFM and Dipartimento di Scienze Fisiche, Universita ` degli Studi di Napoli ‘‘Federico II ’’, Via Cintia, 80126 Napoli, Italy Abstract The resistivity of thin La 0.7 Sr 0.3 MnO 3 films was first investigated in a wide temperature (T ) range (10e 750 K). Films grown by different techniques and on several substrates enabled to analyze samples with different amounts of disorder. The aim of this work was to elucidate the nature of the metaleinsulator (MeI) transition occurring at T ¼ T p in these films and its relation with the different kinds of inhomoge- neities they could present like intrinsic electric disorder and co-existence of two different electrical and/or magnetic phases. The low-temperature resistivity state was described mostly by a law which scales as T a with a z 2.5. This supports the theoretical proposal of single magnon scattering in presence of minority spin states localized by the disorder. In the whole range of temperatures the experimental data are found to be consistent with a phase separation (PS) scenario. In order to go through the origin of the characteristic length scale of inhomogeneity found, preliminarily low frequency noise measurements as a function of T in a range of temperature around the MeI transition were made. The samples used were patterned using photolithography into bridges with various widths and lengths. No clear sign of separation phase dynamic has been observed in our noise measurements. Unexpectedly the normalized Hooge parameter a H /n was * Corresponding author. E-mail address: silvana.mercone@greyc.ensicaen.fr (S. Mercone). 0079-6786/$ - see front matter Ó 2007 Published by Elsevier Ltd. doi:10.1016/j.progsolidstchem.2007.01.035 Progress in Solid State Chemistry 35 (2007) 387e396 www.elsevier.com/locate/pssc