Bratkovsky and Levanyuk Reply:The main new result of our paper [1] is that the ferroelectric (FE) with the dead layer of thickness d is always split into domains, no matter how thin the layer is. We have found that the width of the domains a depends exponentially on d 22 when the dead layer is thin. We have also evaluated the response of the structure to external field (Fig. 2 in [1], and Ref. [2]). In the Comment [3] Tagantsev has tried to interpret our approximate Eq. (14), which he misrepresented as the main result of the Letter, within the "capacitors in series" model, by assuming that the dielectric constant of the FE is infinite, e f `.However, Tagantsev has failed to notice that e f , as found in the "capacitor" model, is not infinite, but finite and actually negative. Indeed, a simple calculation in the capacitor model gives [2]

A novel, general Green's function technique for elastic spin-dependent transport calculations is presented, which (i) scales linearly with system size and (ii) allows straightforward application to general tight-binding Hamiltonians (spd in the present work). The method is applied to studies of conductance and giant magnetoresistance (GMR) of magnetic multilayers in CPP (current perpendicular to planes) geometry in the limit of large coherence length. The magnetic materials considered are Co and Ni, with various non-magnetic materials from the 3d, 4d, and 5d transition metal series. Realistic tight-binding models for them have been constructed with the use of density functional calculations. We have identified three qualitatively different cases which depend on whether or not the bands (densities of states) of a non-magnetic metal (i) form an almost perfect match with one of spin sub-bands of the magnetic metal (as in Cu/Co spin valves); (ii) have almost pure sp character at the * Fermi level (e.g. Ag); (iii) have almost pure d character at the Fermi energy (e.g. Pd, Pt). The key parameters which give rise to a large GMR ratio turn out to be (i) a strong spin polarization of the magnetic metal, (ii) a large energy offset between the conduction band of the non-magnetic metal and one of spin sub-bands of the magnetic metal, and (iii) strong interband scattering in one of spin sub-bands of a magnetic metal. The present results show that GMR oscillates with variation of the thickness of either non-magnetic or magnetic layers, as observed experimentally.

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A novel ferromagnetic transition, accompanied by carrier density collapse, is found in doped chargetransfer insulators with strong electron-phonon coupling. The transition is driven by an exchange interaction of polaronic carriers with localized spins; the strength of the interaction determines whether the transition is first or second order. A giant drop in the number of current carriers during the transition, which is a consequence of bound pairs formation in the paramagnetic phase close to the transition, is extremely sensitive to an external magnetic field. This carrier density collapse describes the resistivity peak and the colossal magnetoresistance of doped manganites. 71.30.+h, 71.38.+i, 72.20.Jv, 75.50.Pp, 75.70.Pa The interplay of the electron-phonon and exchange interactions [1-3] is thought to be responsible for many exotic properties of oxides ranging from high-T c superconductivity in cuprates [4] to colossal magnetoresistance (CMR) and ferromagnetism in doped manganites [5][6][7][8][9]. A huge negative magnetoresistance was observed in doped perovskite manganites La 1−x D x MnO 3 (D=Ca, Sr, Ba) close to the ferromagnetic transition in a certain range of doping x ≈ 0.15 − 0.4 [6][7][8][9], and this raised a question of possible applications.The metal-insulator transition in lanthanum manganites has long been thought to be the consequence of a double exchange (DEX), which results in a varying band width of holes doped into the Mn 3+ d-shell [10], as function of the doping concentration and temperature. Recently it has been realized [11], however, that the effective carrier-spin interaction in DEX model is too weak to lead to a significant reduction of the electron band width and, therefore, cannot account for the observed scattering rate [12] (see also Ref. [13]) or for localization induced by slowly fluctuating spin configurations [14]. In view of this problem, it has been suggested [11] that the essential physics of perovskite manganites lies in the strong coupling of carriers to Jahn-Teller lattice distortions. The argument [11] was that in the high-temperature state the electron-phonon coupling constant λ is large (so that the carriers are polarons) while the growing ferromagnetic order increases the bandwidth and thus decreases λ sufficiently for metallic behavior to set in below the Curie temperature T c . A giant isotope effect [15], the sign anomaly of the Hall effect, and the Arrhenius behavior of the drift and Hall mobilities [16] over a temperature range from 2T c to 4T c unambiguously confirmed the polaronic nature of carriers in manganites.However, an early established unusual relation between magnetization and transport below T c have led to a conclusion that the polaronic hopping is the prevalent conduction mechanism also below T c [17]. Lowtemperature optical [18][19][20], electron-energy-loss (EELS) [21] and photoemission spectroscopies [22] showed that the idea [11,14] of a 'metalization' of manganites below T c is not tenable. A broad incoherent spectral feature [18][19][20]22]...

Here we demonstrate a molecular trap structure that can be formed to capture analyte molecules in solution for detection and identification. The structure is based on gold-coated nanoscale polymer fingers made by nanoimprinting technique. The nanofingers are flexible and their tips can be brought together to trap molecules, while at the same time the gold-coated fingertips form a reliable Raman hot spot for molecule detection and identification based on surface enhanced Raman spectroscopy (SERS). The molecule self-limiting gap size control between fingertips ensures ultimate SERS enhancement for sensitive molecule detection. Furthermore, these type of structures, resulting from top-down meeting self-assembly, can be generalized for other applications, such as plasmonics, meta-materials, and other nanophotonic systems.