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The retention behavior of nanoscale domains in PbZr0.2Ti0.8O3 thin films is investigated by in-situ controlling the epitaxial strain arising from a piezoelectric substrate. The retention behavior in our sample shows strong polarity-dependence: Upward-poled domains exhibit excellent stability, whereas downward-poled domains reveal a stretched exponential decay. Reversible release of in-plane compressive strain strongly reduced the retention loss, reflected in an enhancement of the relaxation time by up to one order of magnitude. We tentatively attribute the observed behavior to a strain dependence of the built-in field at the interface to the La0.7Sr0.3MnO3 bottom electrode, with a possible further contribution of strain-dependent screening of the depolarizing field. Our work directly reveals the importance of epitaxial strain for reducing ferroelectric domain relaxation which is detrimental for applications such as nonvolatile memory devices. [ABSTRACT FROM AUTHOR]

We demonstrate using four-circle x-ray diffraction that the piezoelectric substrate of Pb(Mg1/3Nb2/3)0.72Ti0.28O3(001) induces uniform reversible in-plane strain to epitaxially-grown oxide films and bilayers. The biaxial in-plane strain depends linearly on the applied electrical voltage. Utilizing the reversible strain, the strain-dependent lattice structure and the Poisson number characterizing the elastic response is determined for 200 nm thick SrTiO3, LaScO3, and BiFeO3 films. The uniformity and reversibility of the strain provides access to the direct quantitative measurement of strain-dependent properties of epitaxial oxide films. [ABSTRACT FROM AUTHOR]

The spin-polarized electric transport in ferromagnetic La0.7Sr0.3MnO3 films on piezoelectric substrates with etched steps has been investigated. The Pb(Mg1/3Nb2/3)0.72Ti0.28O3 substrate is strained reversibly by application of electric voltage. This includes strain control in film junctions formed at step edges. The film resistance (R) is very sensitive to both strain and magnetic field in a wide temperature range, 30 K

Epitaxially grown La0.7Sr0.3MnO3 thin films show resistance modulations induced by the inverse piezoeffect of the employed Pb(Mg1/3Nb2/3)O3-PbTiO3(001) (PMN-PT) substrates. The in-plane strain state of the films can continuously be tuned by application of a piezovoltage to PMN-PT. The lattice deformation of a PMN-PT(001) substrate was quantified by x-ray measurements under an electric field. Variation of in-plane lattice parameters by ∼0.06% reversibly changes the resistance of the manganite films by up to 9% at 300 K and shifts the magnetic Curie temperature. Films of different thicknesses from 50 to 290 nm, offering different as-grown strain states, have been studied. [ABSTRACT FROM AUTHOR]

The influence of the bottom electrode's resistance on ferroelectric switching kinetics has been investigated in BiFeO3/La0.8Ca0.2MnO3 capacitors with Pt top contacts. Reversible biaxial strain applied using a piezoelectric substrate is employed to control the resistance of manganite bottom electrode. We found strong dependence of both the switching time and the coercive fields on the electrode's resistance. The reason is attributed to the splitting of the applied voltage between the ferroelectric film and the electrode, which becomes more severe with increasing switching speed. This highlights a crucial limitation for fast switching using lower-conductivity electrodes and inspires the external control of switching kinetics via the electrodes' conductivity. [ABSTRACT FROM AUTHOR]

SrRuO3 films have been grown in the tetragonal, structurally single-domain state under 1% of biaxial tensile strain. The angular dependencies of the magnetization and the magnetoresistance reveal an upright orientation of the tetragonal unit cell and biaxial magnetic in-plane anisotropy with 110t easy axes. Reversible biaxial strain from piezoelectric Pb(Mg1/3Nb2/3)0.72Ti0.28O3 (PMN-PT) substrates has been applied to probe the direct strain response of the magnetization and the electrical resistance. At 1% tensile strain, the Curie temperature (TC) and the ordered magnetic moment (mS) at low temperatures are found to substantially decrease with further growing tensile strain. This suggests a suppression of mS resulting from distortions of the RuO6 octahedra, in line with reported density-functional calculations. Reversible strain has also been applied to a film under weak tensile strain revealing the opposite response, i.e., an enhancement of TC and mS with tensile strain. Structural and magnetic properties of SrRuO3 films in several static strain states (compressive, weak and strong tensile strain) are compared. [ABSTRACT FROM AUTHOR]

We study the effect of elastic anisotropic biaxial strain, induced by a piezoelectric actuator, on the light emitted by neutral excitons confined in different kinds of epitaxial quantum dots. We find that the light polarization rotates by up to ∼80° and the fine structure splitting (FSS) varies nonmonotonically by several tens of μeV as the strain is varied. These findings provide the experimental proof of a recently predicted strain-induced anticrossing of the bright states of neutral excitons in quantum dots. Calculations on model dots qualitatively reproduce the observations and suggest that the minimum reachable FSS critically depends on the orientation of the strain axis relative to the dot elongation. [ABSTRACT FROM AUTHOR]