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Structural and optical effects of the Mn incorporation in Ga IND. 1-x Mn IND. xAs nanocrystalline films prepared by sputtering

Grant number: 05/03463-5
Support Opportunities:Scholarships in Brazil - Master
Effective date (Start): September 01, 2006
Effective date (End): August 31, 2008
Field of knowledge:Engineering - Materials and Metallurgical Engineering - Nonmetallic Materials
Principal Investigator:Jose Humberto Dias da Silva
Grantee:André Luis de Jesus Pereira
Host Institution: Faculdade de Ciências (FC). Universidade Estadual Paulista (UNESP). Campus de Bauru. Bauru , SP, Brazil


The incorporation of Mn to GaAs films has recently attracted great attention due to the demonstrated capacity in producing free holes and associated ferromagnetic characteristics in the Ga(1-x) Mn(x) As compounds (0.3< x <0.6). It is believed that in these materials the holes associated to the presence of Mn+2 are also important to intermediate the ferromagnetic interaction between the Mn ions. These characteristics make the Ga(1-x) Mn(x)As interesting candidates to the development of electronic devices with effective control of spin (spintronics).In this project we are interested in producing and analyzing nanocrystalline Ga(1-x) Mn(x)As films, in order to investigate the influence of different Mn concentrations on the structural, optical and magnetic properties of these materials. The films are being grown by co-sputtering of a GaAs polycrystalline target, covered with different amounts of metallic Mn (small pieces 1mm2). The depositions will be carried using Ar or Ar+H2 atmospheres. Our aim is to investigate the effect of different Mn concentrations on the optic, electric, and magnetic properties of the Ga(1-x) Mn(x)As films prepared by sputtering. Micro-Raman scattering, electronic microanalysis EDX, and grazing incidence X-ray diffraction measurements show that the films are nanostructured, and that there is no evidence for Mn segregation on samples with x < 0.15. Preliminary EXAFS results also show that the Mn atoms probably occupy substitutional lattice sites, in a trend similar to the Mn sites in ferromagnetic Ga(1-x) Mn(x)As. Electrical conductivity measurements, in the absence of magnetic fields, have shown an important increase in the resistivity of some of our samples at temperature around 100K. This temperature approximately corresponds to the ferromagnetic critical temperature of Ga(1-x) Mn(x)As prepared by MBE. Magnetic suscepbility measurements of our samples did not show evidence for ferromagnetic phases in the 300K-2K range. These results indicate that in spite of the lack of ferromagnetic ordering, the local interactions of Mn ions with Ga(1-x) Mn(x)As holes in our samples may be similar to the one observed in the monocrystalline Ga(1-x) Mn(x)As with ferromagnetic behavior.

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Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
PEREIRA, ANDRE L. J.; DA SILVA, J. H. DIAS. Disorder effects produced by the Mn and H incorporations on the optical absorption edge of Ga1-xMnxAs:H nanocrystalline films. Journal of Non-Crystalline Solids, v. 354, n. 52-54, p. 5372-5377, . (05/03463-5, 05/02249-0)
Academic Publications
(References retrieved automatically from State of São Paulo Research Institutions)
PEREIRA, André Luis de Jesus. Efeitos estruturais e ópticos da incorporação de Mn em filmes nanocristalinos de 'Ga IND. 1-x Mn IND. xAs' preparados por sputtering. 2008. Master's Dissertation - Universidade Estadual Paulista (Unesp). Faculdade de Ciências. Bauru Bauru.

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