Statistical switching kinetics in ferroelectrics

By assuming a more realistic nucleation and polarization reversal scenario we build a new statistical switching model for ferroelectrics, which is different from either the Kolmogorov-Avrami-Ishibashi (KAI) model or the Nucleation-Limited-Switching (NLS) model. After incorporating a time-dependent depolarization field this model gives a good description about the retardation behavior in polycrystalline thin films at medium or low fields, which can not be described by the traditional KAI model. This model predicts correctly n=1 for polycrystalline thin films at high Eappl or ceramic bulks in the ideal case

Orientation dependence of ferroelectric properties of pulsed-laser-ablated Bi4-xNdxTi3O12 films

Epitaxial (001)-, (118)-, and (104)-oriented Nd-doped Bi4Ti3O12 films have been grown by pulsed-laser deposition from a Bi4-xNdxTi3O12 (x=0.85) target on SrRuO3 coated single-crystal (100)-, (110)-, and (111)-oriented SrTiO3 substrates, respectively. X-ray diffraction illustrated a unique epitaxial relationship between film and substrate for all orientations. We observed a strong dependence of ferroelectric properties on the film orientation, with no ferroelectric activity in an (001)-oriented film; a remanent polarization 2P(r) of 12 muC/cm(2) and coercive field E-c of 120 kV/cm in a (118)-oriented film; and 2P(r)=40 muC/cm(2), E-c=50 kV/cm in a (104)-oriented film. The lack of ferroelectric activity along the c-axis is consistent with the orthorhombic nature of the crystal structure of the bulk material, as determined by powder neutron diffraction. (C) 2003 American Institute of Physics

Folding catastrophes due to viscosity in multiferroic domains : implications for room-temperature multiferroic switching

Unusual domains with curved walls and failure to satisfy the Landau–Lifshitz-Kittel Law are modeled as folding catastrophes (saddle-node bifurcations). This description of ballistic motion in a viscous medium is based upon early work by Dawber et al 2003 Appl. Phys. Lett . 82 436. It suggests that ferroelectric films can exhibit folds or vortex patterns but not both.Publisher PDFPeer reviewe

Non‐restrictive interventions to reduce self‐harm amongst children in mental health inpatient settings: Systematic review and narrative synthesis

Rates of self-harm amongst children appear to be increasing. This presents challenges for practitioners responsible for maintaining the safety of children admitted to mental health inpatient settings. Policy guidelines recommend that practitioners should aim to avoid the use of restrictive practices for children. It is currently unclear, however, what evidence-based alternatives to restrictive practices are available. We aimed to identify what non-restrictive interventions have been proposed to reduce self-harm amongst children in mental health inpatient settings and to evaluate the evidence supporting their use in clinical practice. A systematic search of five databases (CINAHL, Embase, Ovid MEDLINE, APA Psycinfo, and Cochrane) was conducted to identify articles reporting on non-restrictive interventions aimed at reducing self-harm amongst children in mental health inpatient settings. Articles were quality assessed and relevant data were extracted and synthesized using narrative synthesis. Searches identified relatively few relevant articles (n = 7) and these were generally of low methodological quality. The underlying theoretical assumptions and putative mechanisms of change for the interventions described were often unclear. Despite concerns about the rates of self-harm amongst children in mental health inpatient settings, there is a lack of high-quality research to inform clinical practice. There is an urgent need to develop effective non-restrictive interventions aimed at reducing self-harm for children using inpatient mental health services. Intervention development should be theoretically informed and be conducted in collaboration with people who have lived experience of this issue

Combining half-metals and multiferroics into epitaxial heterostructures for spintronics

We report on the growth of epitaxial bilayers of the La2/3Sr1/3MnO3 (LSMO) half-metallic ferromagnet and the BiFeO3 (BFO) multiferroic, on SrTiO3(001) by pulsed laser deposition. The growth mode of both layers is two-dimensional, which results in unit-cell smooth surfaces. We show that both materials keep their properties inside the heterostructures, i.e. the LSMO layer (11 nm thick) is ferromagnetic with a Curie temperature of ~330K, while the BFO films shows ferroelectricity down to very low thicknesses (5 nm). Conductive-tip atomic force microscope mappings of BFO/LSMO bilayers for different BFO thicknesses reveal a high and homogeneous resistive state for the BFO film that can thus be used as a ferroelectric tunnel barrier in tunnel junctions based on a half-metal