electric field: induced

https://doi.org/10.1016/0030-4018(76)90450-8 Access and use of this website and the material on it are subject to the Terms and Conditions set forth at Electric field induced shifting of optical holes, fluorescence line narrowing and free induction decay in ruby

CONCLUSION In this work, we demonstrated that taking advantage of the electric field-induced bacterial aggregation allows determining the stoichiometry and the binding site constant between polycation ligands and bacteria, by direct analysis of equilibrated mixtures using frontal analysis continuous capillary electrophoresis. This methodology does not require any filtration step nor sample treatment. The model of independent sites of equal energy was used to determine DGL-bacteria binding site constant k in the order of ∼10 6 −10 7 M −1 . Ligandsubstrate stoichiometries decrease with DGL generation

Supporting Information Electric-field Induced Reversible Switching of the Magnetic Easy-axis in Co/BiFeO 3 on SrTiO 3 Tieren Gao 1 , Xiaohang Zhang 1,2 , William Ratcliff II 3 , Shingo Maruyama 1 , Makoto Murakami 1 , Anbusathaiah Varatharajan 4 , Zahra Yamani 5 , Peijie Chen 2 , Ke Wang 2 , Huairuo Zhang 6,2 , Robert Shull 2 , Leonid A. Bendersky 2 , John Unguris 7 , Ramamoorthy Ramesh 8 , and Ichiro. Takeuchi 1,*

was observed. For this reason we used the modulus formalism for separating interfacial phenomena from dipole relaxation due to charge hopping. For further investigation of eventual grain boundary effects on the complex conductivity of this material, we have investigated a single crystal sample of RbMn[Fe(CN) 6 ].H 2 O as well (sample 5). [ vertelman 08] Due to the small size (ca. 1 mm 3 ) and non-geometrical shape of the available crystals the electrode geometry is ill-determined and this leads to high uncertainty in the absolute value of the conductivity and also to higher standard deviation of the data, especially at low temperatures. Nevertheless, the conductivity data on single crystals resembles closely to those obtained on polycrystalline samples (Figure II.3 e). Notably, we noticed a marked deviation from an Arrhenius-type behavior below 220 K. Between 350 and 220 K the conductivity falls four orders of magnitude, similar to the polycrystalline case, which corresponds to a thermal activation energy of ca. 0.52 eV (table 1). Note here that in the single crystals the phase transition takes place rather gradualy between the pure HT phase and a mixed (1:1) HT+LT form and therefore fitting cannot be carried out in the LT phase. However, it appears clearly that both the relaxation frequency and the conductivity of the LT form are higher when compared to the pure HT phase (at a given temperature). The frequency dependence of the conductivity follows a power law and, as a consequence, the hysteresis of the conductivity disappears at higher frequencies. The electric loss moduli M”( ω ) exhibit temperature dependent relaxation maxima and the M”( ω ) curves at different temperatures can be scaled to a master curve similar to the powder samples. The activation energy of the relaxation is ca. 0.50 eV. This means that in the crystals as well the relationship E dc ≅ E p is confirmed. The

The error on the calculation of the dielectrophoretic force magnitude is generally under 20% in the region of interest. This correlation is in accordance with Green’s work, [ 29 ], which compares Fourier series and FEM for traveling wave with linear approximation of the boundary condition. These two works, Green’s and ours are less accurate than the approach proposed by Song et al. [ 26 ]. Song improves the accuracy near the electrode using an artificial neural network to break down the boundary conditions, allowing to compute higher orders of the Fourier series. However, for automation application, 20% of error in the field magnitude can easily be corrected using closed-loop and the priority is given to the simplicity of the model.

migrated would not likely take a crystalline form that can be detected by XRD which is the reason that no other species are observed in the GIXRD patterns. If the primary mechanism underlying the magnetic changes observed here are from oxygen migration, then we would also expect to see changes in the electric properties. To probe this, we investigated the electronic properties using Current Atomic Force Microscopy (CAFM) and the results are shown in Fig.  10 . We performed a 3D representation of the obtained data, in which the colors represent the current value recorded while the roughness corresponds to the real topography of the sample. From the initial sample, we were not able to record any current flowing through the system, see “State I” graph. However, after being treated at −10 V for 120 min, see “State III”, we were able to record a current distribution map. We see that the bottom part of the topography is responsible for the change in the current level recorded, while the top topography features remains unaltered. This increase in current flow is consistent with oxygen ion migration causing oxygen redistribution. With a more heterogenous distribution, there should be some areas that are oxygen deficient (i.e., have many oxygen vacancies) and are therefore better able to conduct the electrons. Next, the sample was treated at +10 V for 120 min, see “State IV”, which returned the current level very close to the initial state-the minimum that our equipment can resolve. This is again consistent with the magneto-ionic mechanism since the positive voltage is expected to return the sample to a more homogeneous oxygen distribution similar to the initial state. Topographically, we do not observe appreciable changes. State I is very flat while state III and IV have some peaks. We believe that there is a bit additional roughness induced by the oxygen migration process which causes these local peaks. Purely topographical images can be found in the Supplementary Information, Fig. S1. From the current data, we performed pixel histograms for each of the three samples, see Fig.  10b . We found that the current level for the −10 V treated sample is almost two orders of magnitude higher than the initial state and +10 V cases which corresponds to a decrease in electronic resistivity. Examples of I-V spectroscopy curves of the initial and −10 V treated sample, as a com- parison, in random spots of the surface are shown in Fig.  10c . The reader may note spikes occurring at the exact same position for both states (I and III). These spikes result from an electronic artifact inherent to our measuring conditions. Such spikes should not be interpreted with a physical meaning underneath, instead they should be attributed to changes into the gain value of our variable dynamic range of the transimpedance amplifier (TIA) used.

insulator to metal transition. Interestingly, recent theoretical works predict that an electric field can break the Mott insulating state [3,4,5] and induce an insulator to metal transition. The RS observed in the AM 4 X 8 compounds might be the first example of such a transition. These compounds could therefore offer the possibility to explore a new type of RRAM based mostly on an electronic phase change, that we could call a Mott-RRAM. First results obtained on the AM 4 X 8 compounds are promising showing fast writing / erasing times (down to 50 ns) and

ABSTRACT: Electric-field (E-field) control of magnetism enabled by multiferroic materials has the potential to revolutionize the landscape of present memory devices plagued with high energy dissipation. To date, this E-field controlled multiferroic scheme has only been demonstrated at room temperature using BiFeO 3 fi lms grown on DyScO 3 , a unique and expensive substrate, which gives rise to a particular ferroelectric domain pattern in BiFeO 3 . Here, we demonstrate reversible electric-field-induced switching of the magnetic state of the Co layer in Co/BiFeO 3 (BFO) (001) thin film heterostructures fabricated on (001) SrTiO 3 (STO) substrates. The angular dependence of the coercivity and the remanent magnetization of the Co layer indicates that its easy axis reversibly switches back and forth 45° between the (100) and the (110) crystallographic directions of STO as a result of alternating application of positive and negative voltage pulses between the patterned top Co electrode layer and the (001) SrRuO 3 (SRO) layer on which the ferroelectric BFO is epitaxially grown. The coercivity (H C ) of the Co layer exhibits a hysteretic behavior between two states as a function of voltage. A mechanism based on the intrinsic magnetoelectric coupling in multiferroic BFO

2 Although efficient lead-free piezoelectric thin films have been recently proposed in the literature [1- 4], lead-based films as Pb(Zr,Ti)O 3 (PZT) [5,6] or Pb(Mg,Nb)O 3 -PbTiO 3 (PMN-PT) [7] always exhibit the best piezoelectric properties. More specifically, they are strongly enhanced at the so-called morphotropic phase boundary (MPB) [8]. For PZT, the MPB is at the interface between the tetragonal and rhombohedral phases while Zr/Ti atomic ratio is close to 52/48. In addition to these phases, the monoclinic phase might be present in the MPB, as evidenced in 1999 by Noheda et al. [9]. This phase coexistence and consequently the polarization mobility increase are thought to be the reason why piezoelectricity is enhanced in the MPB region. In 2011, Hinterstein et al. showed by in situ observations that bulk ceramic MPB PZT experiences structural changes while an electric field is applied [10]. More specifically, they reported that the application of an electric field reveals an increase of the monoclinic phase fraction. As they observed that most of PZT was composed of tetragonal and monoclinic phases, it strongly suggests that PZT experienced a tetragonal-to- monoclinic phase transition under electric field, and not only rotation of the polarization. An open question is therefore whether there is a correlation between large piezoelectric effects and this field- induced phase transition. Today, it is widely believed that most of the piezoelectric effect is induced by domain walls switching. It is the so-called extrinsic contribution [11]. Several groups showed that PZT bulk and thin films in the tetragonal phase experience a to c domain switching while electric field is applied [12-15]. In this paper, we show in situ structural modifications in MPB PZT films versus electric field and compare with their piezoelectric properties. We aim to correlate field-induced phase transition and piezoelectric properties. This correlation could have a strong impact on piezoelectric material design for applications, as inkjet devices, integrated optical lenses or micro- actuators in general [16].

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II. TIGHT-BINDING MODEL Figure 1(a) shows two possibilities for building a bi- layer triangular graphene quantum dot (BTGQD) using two single-layer triangular quantum dots (TGQDs) of comparable sizes, with zigzag edges. The stability of TGQDs to defects was established in Refs. 17 and 18 . We consider AB Bernal stacking, where the A sublattice of the top layer (A2, shown in blue color online) is on top of the B sublattice of the bottom layer (B1, shown in red color online). On the left hand side, the two TGQDs are of the same size. In this configuration, however, not all the A2 atoms have a B1 partner as required by Bernal stacking. A more natural configuration choice is shown on the right hand side of Fig. 1(a) . The top layer triangle has its floating atoms removed, making it smaller than the bottom layer triangle. Such a bilayer construction has the interesting property of having an odd number of degenerate states at the Fermi level independent of its size, allowing to isolate a single spin in a charge neutral structure. This is illustrated in Fig. 1(b) , where the spin density isosurfaces are shown for zero electric field (left hand side) and finite electric field (right hand side), as obtained from our tight-binding-based configuration interaction calculations explained in detail in Sec. IV . When the electric field is off, both layers have a finite magnetic moment, as in single layer triangles, 14 – 20

We increase the incident intensity on the quartz plate, with the polarization perpendicular to the crystal axis to generate a second harmonic. With I peak  4 × 10 13 W∕cm 2 (near the damage threshold), we expect little energy deposited to the sample [ 26 ]. We now find that the interference fringes are not linear as a func- tion of the CEP. The measured visible spectrum is shown in Fig. 4(a) , while a 1D calculation is shown in Fig. 4(b) . The spec- tral modulation now has a nonlinear dependence on the input CEP. Over certain values of the CEP, the spectral modulation becomes less dependent on the driving field CEP (shown by the black line in the insets). This spectral modulation, which rep- resents a measurement of the pulse phase, signifies that after propagating through the quartz the resulting phase is nonlinearly correlated to the driving field CEP.

Interestingly, it appears that some hitherto unknown atmo- spheric process counteracts gravitational settling of larger at- mospheric dust particles (Maring et al., 2003), as models of long-range dust transport often underestimate the larger par- ticle fraction (Colarco et al., 2003, Ginoux et al., 2001), and dust samples collected after fallout events show that large numbers of “giant” dust particles (>62.5 µm) can be car- ried thousands of kilometers from their source (Middleton et al., 2001). In principle, aggregation of smaller particles might shift the size distribution towards larger sizes and in our context it may be relevant that aggregation of aerosol particles can be enhanced by charging under some circum- stances (Clement et al., 1995). It is also possible that the settling is counteracted to some extent by the electric field itself, provided that gravitational separation of positively and negatively charged particles is taking place, leading to the emergence of a dipole. In effect, particles with oppo- site charges might then become coupled by attractive forces. Such coupling could effectively increase the projected area of larger aerosol particles, slowing down their settling. Ex- amination of the size distribution in Fig. 5 shows that this “electrostatically-mediated aerodynamic breaking” could be

4 EXPERIMENTAL RESULTS In order to measure the interaction between both antennas, two perfectly identical half-wave anten- nas are used, which makes inter-antenna distance measurement easier. Each dipole is fastened on a micrometric mechanism allowing an accurate measurement of the distance between the antennas, which is swept between 1 and 19 mm. In order to trigger both near- and far-field interactions, the antennas are fed with a high-frequency (27.5 GHz) generator; consequently, the far-field criterion is met at approximately 3.5 mm ( λ π ).

A similar dissociation process was observed in a Co sample with 150 nm wire width, figure 4 (b), except that the field steps did not capture the presence of two separate 180DWs in the wire[r]

The Jahn-Teller distortion, by its very nature, is often at the heart of the various electronic properties displayed by perovskites and related materials. Despite the Jahn-Teller mode being nonpolar, we devise and demonstrate, in the present Letter, an electric field control of Jahn-Teller distortions in bulk perovskites. The electric field control is enabled through an anharmonic lattice mode coupling between the Jahn-Teller distortion and a polar mode. We confirm this coupling and quantify it through first-principles calculations. The coupling will always exist within the Pb 2 1 m space group, which is found to be the favored ground state for various perovskites under sufficient tensile epitaxial strain. Intriguingly, the calculations reveal that this mechanism is not only restricted to Jahn-Teller active systems, promising a general route to tune or induce novel electronic functionality in perovskites as a whole.

B. Electroluminescence under AC stress In view of the large space charge effects likely to occur in PEN at high fields, it is interesting to consider the case of AC stress. The effect of frequency on the EL phase patterns has been investigated along with the EL-field characteristics. A feature of EL under ac stress, not specific to PEN, is the occurrence of surface plasmons emission when using gold electrodes [32]. Recent characterization achieved using ITO electrodes allows getting rid of these effects [33]. Typically EL-field characteristics obtained on PEN are shown in Fig. 9. Compared to DC stress, the EL threshold is found at at a much lower field (about 30 kV/mm), and the increase of the EL with field is much milder. The EL is in advance in respect to the peak voltage; the advance of phase tends to decrease with increasing the field (from 18° to 9° when going from 160 to 270 kV/mm). The EL under AC is controlled by the recombination of injected carriers and trapped carriers with opposite charges. Injected charges either are trapped or recombine with trapped carriers of opposite polarity from last half field cycle, generating advance of EL peak. Compared to

different field enhancements would exhibit damage thresholds related to their electric field maximum. We address this issue using MLD gratings with 1780 l/mm . Section 2 provides a description of the numerical method developed to optimize the MLD gratings. It is able to accurately solve Maxwell equations in periodic devices with a trapezoidal modulation. Manufacturer capabilities as well as grating specification and electric field value inside the MLD stack are taken into account. Section 3 is devoted to the damage testing setup we have built. The facility called DERIC is able to damage test the part at the wavelength of 1057nm with pulse duration of 500 fs. 1/1 and S/1 damage testing procedure can be performed. Testing is carried out in dry or wet environment depending of part specifications. Section 4 presents the various MLD parts we manufactured. Both theoretical and controlled grating groove profiles are given. Diffraction efficiency was also measured. Finally, section 5 details the obtained results. Discussions presented in section 6 demonstrate that the damage threshold is related to the electric field intensity value in the MLD grating.

e=6.5). It this case, there are two main reasons to induce a field divergence. The first one is related to the sharp edge of the Cu metallization that strongly enhances the electric field at the closest facing electrode tips by a pure geometrical effect (i.e tip-to-tip configuration). By this sharp-edge effect, the field is also enhanced around the top corners of the Cu tracks. On the other hand, the electric field divergence is further enhanced at the electrode tips by the ‘triple point’ effect where the junction of three different materials with different dielectric properties (i.e. metal, ceramic and composite) is located. The electric field around the HV electrode (Figure 3) is higher because there is the bottom electrode of the DBC connected at the ground potential (Figure 2b).

After 17 days, the pH in cells C50 and C75 is similar and homogeneous but not in cell C25 because of the slower front advance. In this case, all the medium is not at the basic pH necessary for fluorine solubilisation. The electromigration treatment on the C25 cell was carried on up to 39 days [11], in order to attain the similar homoge- neous pH obtained in cells C50 and C75 (Fig. 3(a)). The pH front advance is a function of the applied electric potential and so, in order to attain the complete pollutant solubilisation in a time defined and to have a chemical pseudo steady state, an threshold electric potential must be ap- plied between the electrodes.