One of the most exciting feature of manganites thin films is the close correlations between the electronic transport and the strain effect induced by the substrate used for thin films growth. In fact the physical properties of the films (TI-M, TC, MR) - PowerPoint PPT Presentation

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One of the most exciting feature of manganites thin films is the close correlations between the electronic transport and the strain effect induced by the substrate used for thin films growth. In fact the physical properties of the films (TI-M, TC, MR)

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One of the most exciting feature of manganites thin films is the close ... (XRD) data were collected by using a Bruker 'D8 Advance' diffractometer. ... – PowerPoint PPT presentation

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Title: One of the most exciting feature of manganites thin films is the close correlations between the electronic transport and the strain effect induced by the substrate used for thin films growth. In fact the physical properties of the films (TI-M, TC, MR)


1
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2
Introduction
  • One of the most exciting feature of manganites
    thin films is the close correlations between the
    electronic transport and the strain effect
    induced by the substrate used for thin films
    growth. In fact the physical properties of the
    films (TI-M, TC, MR) can be nicely tuned by
    controlling the film thickness and the substrate
    nature, i.e., the two most important variable in
    affecting the film strain and growth direction.
  • Recently we focused on the sodium doped lanthanum
    manganites in order to deeply investigate this
    system which looks suitable for achieving better
    electronic and magnetic properties. This is
    mainly due to the fact that the tolerance factor
    (t) is practically unchanged by the sodium
    replacement of lanthanum moreover, compared to
    the Ca-doped manganites, it is possible to
    achieve an equal amount of hole doping with a
    lower cation substitution since for the same
    amount of aliovalent dopant the hole density is
    twice with respect to the calcium doping. This
    should reflect in a lower cation disorder induced
    by the doping. Finally, for an optimal doping,
    these materials present a rhombohedral structure.

3
Experimental
  • La0.88Na0.12MnO3? thin films were deposited on
    SrTiO3 (100), NdGaO3 (100) and NdGaO3 (110)
    single crystals. The depositions were performed
    by an off-axis Rf-magnetron sputtering system.
  • X-ray reflectivity (XRR), as well as ?-2? X-ray
    diffraction (XRD) data were collected by using a
    Bruker D8 Advance diffractometer.
  • Resistance measurements were carried out in a
    Quantum Design Magnetic Property Measurement
    System (MPMS) in a four points configuration.
  • NC-AFM images were obtained with an Autoprobe CP
    microscope (Park Instruments- VEECO), operating
    in non-contact mode.

4
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5
Film growth and microstructure
6
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7
Substrate induced strain
  • The strain is defined as ((asubstrate-atarget)/asu
    bstrate)?100
  • For the STO (100) substrate is about 0.50
    (tensile strain).
  • For the NGO (110) substrate is about -0.54
    (compressive strain)
  • Finally, for the films grown on the NGO (100),
    the epitaxial growth should place the b-c lattice
    planes of the orthorhombic Pbnm structure in the
    plane of the substrate while the out-of-plane
    lattice constant will be one of the two short
    axes of the orthorhombic cell (a, in this case)

8
Magnetoresistance STO (100) deposited films
9
Magnetoresistance NGO (110) deposited films
10
Magnetoresistance NGO (100) deposited films
11
Conclusions
  • The first synthesis by means of Rf-sputtering of
    optimally doped La1-xNaxMnO3 thin films has been
    performed, With three different substrates, and
    for each of them, three different thicknesses.
  • The synthetic procedure here applied showed to be
    suitable to produce well oriented epitaxial thin
    films.
  • The structural data showed that film grown onto
    STO (100) are under tensile strain while the one
    growth on NGO (110) are under a compressive
    strain of the same magnitude.
  • Films grown onto the NGO (110) substrate do not
    show magnetoresistance.
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