Beatriz Noheda

Publications (6)0 Total impact

• Source

  Available from: ArXiv

  Article: Fine tuning epitaxial strain in ferroelectrics: PbxSr(1-x)TiO3 on DyScO3

  Gijsbert Rispens, Jeroen A. Heuver, Beatriz Noheda
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  ABSTRACT: Epitaxial strain can be used to modify the properties of ferroelectric thin films. From the experimental viewpoint, the challenge is to fine-tune the magnitude of the strain. We illustrate how, by using a suitable combination of composition and substrate, the magnitude of the epitaxial strain can be controlled in a continuous manner. The phase diagram of PbxSr1-xTiO3 films grown epitaxially on (110)-DyScO3 is calculated using a Devonshire-Landau approach. A boundary between in-plane and out-of-plane oriented ferroelectric phases is predicted to take place at $x \approx$ 0.8. A series of PbxSr1-xTiO3 films grown by MBE show good agreement with the proposed phase diagram Comment: The following article has been submitted to Applied Physics Letters
  11/2010;
• Source

  Available from: ArXiv

  Article: Domain wall magnetism in thin films of orthorhombic manganites

  Christophe J. M. Daumont, Sriram Venkatesan, Bart J. Kooi, Jeff Th. M. De Hosson, Beatriz Noheda
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  ABSTRACT: Thin films of orthorhombic TbMnO$_3$, as well as other orthorhombic manganites, epitaxially grown on cubic SrTiO$_3$ substrates display an induced magnetic moment that is absent in the bulk (antiferromagnetic) counterpart. Here we show that there is a clear correlation between the domain microstructure and the induced magnetic moment in TbMnO$_3$ films on SrTiO$_3$. In addition, the distinct dependence of the magnetization with the film thickness is not consistent with domain magnetism and indicates that the domain walls, rather than the domains, are the origin of the net magnetic moment. Since the orientation of the domain walls can be designed by the film-substrate relationship and its density can be tuned with the film thickness, these results represent a significant step forward towards the design of devices based on domain wall functionality. Comment: 5pages, 3figures (color online). Revised version including estimation of domain wall magnetization; reference to Salje et al. and Malozemoff added; title revised. Other minor changes made overall
  08/2010;
• Source

  Available from: rug.nl

  Article: Monodomain strained ferroelectric PbTiO_ {3} thin films: Phase transition and critical thickness study

  Sriram Venkatesan, Ard Vlooswijk, Bart J. Kooi, Alessio Morelli, George Palasantzas, Jeff T. M. De Hosson, Beatriz Noheda
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  ABSTRACT: This work demonstrates that instead of paraelectric PbTiO3, completely c-oriented ferroelectric PbTiO3 thin films were directly grown on (001)-SrTiO3 substrates by pulsed-laser deposition with thickness up to 340 nm at a temperature well above the Curie temperature of bulk PbTiO3. The influence of laser-pulse frequency, substrate-surface termination on growth, and functional properties were studied using x-ray diffraction, transmission electron microscopy, and piezoresponse force microscopy. At low growth rates (frequency <5 Hz) the films were always monodomain. However, at higher growth rates (frequency >8 Hz) a domains were formed for film thickness above 20–100 nm. Due to coherency strains the Curie temperature (Tc) of the monodomain films was increased approximately by 350 °C with respect to the Tc of bulk PbTiO3 even for 280-nm-thick films. Nonetheless, up to now this type of growth mode has been considered unlikely to occur since the Matthews-Blakeslee (MB) model already predicts strain relaxation for films having a thickness of only ∼10 nm. However, the present work disputes the applicability of the MB model. It clarifies the physical reasons for the large increase in Tc for thick films, and it is shown that the experimental results are in good agreement with the predictions based on the monodomain model of Pertsev et al. Phys. Rev. Lett. 80 1988 (1998).
  Phys. Rev. B. 09/2008; 78(10).
• Source

  Available from: arxiv.org

  Article: Thin Lead Titanate films grown by Molecular Beam Epitaxy

  Gijsbert Rispens, Beatriz Noheda
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  ABSTRACT: The growth of atomically-flat thin films of ferroelectric PbTiO3 on SrTiO3 substrates, using molecular beam epitaxy, is reported. The main issue in the growth of these materials is the high volatility of lead. This can be largely overcome by using PbO, instead of Pb, as a source and by using atomic oxygen during growth. The continuous decrease of the out-of-plane lattice parameter with increasing temperature in the investigated range, indicates that PbTiO3 is still ferroelectric at the growth temperature (Tg= 600oC), which agrees with the theoretical prediction of TC= 765oC (compared to TCbulk= 490oC) for the present mismatch strain values.
  05/2007;
• Source

  Available from: rug.nl

  Article: Ultra-Thin Lead Titanate Films Grown by Molecular Beam Epitaxy

  Gijsbert Rispens, Beatriz Noheda
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  ABSTRACT: The growth of atomically-flat thin films of ferroelectric PbTiO3 on SrTiO3 substrates, using molecular beam epitaxy, is reported. The main issue in the growth of these materials is the high volatility of lead. This can be largely overcome by using PbO, instead of Pb, as a source and by using atomic oxygen during growth. The continuous decrease of the out-of-plane lattice parameter with increasing temperature in the investigated range (RT-650°C), indicates that the films are still ferroelectric at the growth temperature (Tg = 600°C), as expected according to the theoretical prediction of TC = 765°C (compared to TbulkC = 490°C) for the present mismatch strain values.
• Source

  Available from: Christophe Daumont

  Article: Nanoscale domain evolution in thin films of multiferroic TbMnO3

  Sriram Venkatesan, Christophe Daumont, Bart J. Kooi, Beatriz Noheda, Jeff Th.M. De Hosson
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  ABSTRACT: Control of the domain structures in multiferroic thin films is of crucial importance in order to gain access to their functional responses. Here we report on the evolution of the nanodomain structures observed in epitaxial thin films of multiferroic TbMnO3 grown on SrTiO3 substrates. Thin films with thickness ranging from 2 to 140 nm were grown at 0.25 and 0.9 mbar oxygen partial pressures. Transmission electron microscopy was employed to study and understand the domain evolution. A transition from a fully coherent, highly strained, tetragonal film to a partially coherent, distorted, orthorhombic structure occurs via a transformation twinning mechanism, giving rise to four different domain orientations. Then, at larger thicknesses, a transition to the fully relaxed orthorhombic structure occurs via changes in the domain-substrate orientation relationships leading to only two domain variants. Differences have been observed in the strain relaxation behavior for films grown at different oxygen pressures. All the observations have allowed us to understand the evolution of the domain structures and to accurately explain the measured orthorhombic distortion. This mechanism can be generalized for [001]-oriented orthorhombic perovskites grown on cubic substrates with large misfit values.