Alignment of energy levels at the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Al</mml:mi><mml:msub><mml:mi mathvariant="normal">q</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:mo>∕</mml:mo><mml:msub><mml:mi mathvariant="normal">La</mml:mi><mml:mn>0.7</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">Sr</mml:mi><mml:mn>0.3</mml:mn></mml:msub><mml:mi mathvariant="normal">Mn</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn

Zhan, Yiqiang; Bergenti, I.; Hueso, Luis E.; Dediu, V.; Jong, M. P. de; Li, Z. S.

doi:10.1103/physrevb.76.045406

Cited by 76 publications

(46 citation statements)

References 40 publications

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“…This could be a relevant consideration for understanding the orientation of dipolar molecules deposited on the surface. Spin valve devices based in LSMO have already been demonstrated with Alq3 (8-hydroxy-quinoline aluminum) [27], and a substantial shift in its molecular energy levels has been measured [28]. Our results suggest that the observed lowering of the molecular energy levels is caused by the electrostatic potential resulting from the orientation of the Alq3 molecular dipole by the LSMO surface dipole.…”

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confidence: 48%

Ferrodistortive Instability at the (001) Surface of Half-Metallic Manganites

et al. 2007

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We present the structure of the fully relaxed (001) surface of the half-metallic manganite La 0:7 Sr 0:3 MnO 3 , calculated using density functional theory. Two relevant ferroelastic order parameters are identified and characterized. The known tilting of the oxygen octahedra, which is present in the bulk phase, decreases towards the surface. A ferrodistortive Mn off-centering, triggered by the surface and not reported before, decays monotonically into the bulk. This distortion affects neither the half-metallicity nor the zero-temperature magnetization, but does change the effective spin-spin interactions, and thus the temperature dependence of the magnetic properties. DOI: 10.1103/PhysRevLett.99.226101 PACS numbers: 75.70.ÿi, 73.20.ÿr, 75.47.Lx A delicate balance between structure and physical properties in perovskites makes this family of materials interesting scientifically and of technological importance. In addition to high-T C superconductors, most of the inorganic ferroelectric and piezoelectric materials belong to this family, with an important presence in the growing field of multiferroics [1]. Manganites are prominent members of this family since the discovery of colossal magnetoresistance [2]. Within an extremely rich phase diagram, the optimally doped La 1ÿx A x MnO 3 (A Sr, Ca) phase, obtained for x 0:3, is of particular interest because of its half-metallicity, i.e., with a gap for one spin direction and thus with fully spin-polarized carriers, extremely useful for spintronics.A fundamental obstacle for the development of manganite devices is the fact that some of the physical properties of the surface markedly deviate from those of the bulk. Electron-lattice interactions are known to play an important role in the electronic properties of these oxides [3], making it thus crucial to characterize the structural distortions at the surface, which are so far unknown. The primary goal of this work is to determine the structural changes induced by surface termination at the (100) surface of La 0:7 Sr 0:3 MnO 3 (LSMO) and the influence of these structural changes on the electronic properties for the clean surface. The effect of oxygen vacancies, as prototypical imperfections, is briefly discussed at the end.The theoretical description of manganites is challenging given the strong correlations of the transition metal d electrons, as well as the complex chemistry and large range of possible structural distortions characteristic of perovskites. Ab initio studies to date have been confined to experimental crystal parameters or pseudocubic structures [4,5], partly because a full description of structure and doping represents a substantial increase of the computational needs, but also because the lattice parameters obtained at the time were in poor agreement with experiments.Here, we present ab initio results for a fully relaxed LSMO (001) surface obtained using density-functional theory (DFT) within the generalized gradient approximation (GGA). Our choice of exchange-correlation functional was motivated by o...

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confidence: 48%

Ferrodistortive Instability at the (001) Surface of Half-Metallic Manganites

et al. 2007

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“…Strong electrical dipoles are present at many OSC/metal interfaces and these interfacial dipoles can significantly alter the non-interacting equilibrium energy levels 11,13,14,[22][23][24][25][26][27][28] . Thus far, little is experimentally known about the role of these vacuum level shifts on spin injection and extraction.…”

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confidence: 99%

Engineering spin propagation across a hybrid organic/inorganic interface using a polar layer

et al. 2010

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Spintronics has shown a remarkable and rapid development, for example from the initial discovery of giant magnetoresistance in spin valves 1 to their ubiquity in hard-disk read heads in a relatively short time. However, the ability to fully harness electron spin as another degree of freedom in semiconductor devices has been slower to take off. One future avenue that may expand the spintronic technology base is to take advantage of the flexibility intrinsic to organic semiconductors (OSCs), where it is possible to engineer and control their electronic properties and tailor them to obtain new device concepts 2 . Here we show that we can control the spin polarization of extracted charge carriers from an OSC by the inclusion of a thin interfacial layer of polar material. The electric dipole moment brought about by this layer shifts the OSC highest occupied molecular orbital with respect to the Fermi energy of the ferromagnetic contact. This approach allows us full control of the spin band appropriate for charge-carrier extraction, opening up new spintronic device concepts for future exploitation.The development and understanding of new hybrid organic/inorganic interfaces will enable considerable progress in organic spintronics for technological purposes, including processing elements, sensors, memories and conceptually different future applications. In addition to the 'standard' spintronic applications, newly developed interfaces could bring spintronic effects to the field of organic light-emitting diodes (OLEDs), as well as in the fast progressing field of organic field-effect transistors. For example, the injection of carriers with a controlled spin state could enable the amplification of either singlet or triplet exciton states 2 leading to a significant increase in the efficiency of the electroluminescence in OLEDs. Although these considerations are conceptually straightforward, no efficiency amplification has yet been reported in the literature, despite several attempts 3 . The failure of those approaches was caused by the simple reason that light emission can be detected starting from an applied voltage of a few volts, whereas state-of-the-art spin injection in organic materials persists to a maximum of around 1 V (refs 4-6). As yet, this is unexplained. Further complications arise from the fact that various reports on working devices show a wide spread of performances for apparently similar structures, highlighting the issue of reproducibility [7][8][9] . The poor reproducibility is mainly due to the unknown interplay between processing and spin transfer performance and there is little deterministic control of the interface properties. However, it has recently been demonstrated that the insertion of a barrier

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“…Caruso suggested the adsorption geometry of the Alq 3 on Au and Co must be different to produce a perturbation in the molecular orbitals. Zhan et al [22,23] used UPS and X-ray photoelectron spectroscopy (XPS) to characterize the adsorption of Alq 3 on LSMO and Co. They found that the work function of LSMO and Co decreased by 0.9 and 1.4 eV, respectively, upon adsorption of Alq 3 .…”

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The role of interfaces in organic spin valves revealed through spectroscopic and transport measurements

Drew

Szulczewski

Nuccio

et al. 2011

Physica Status Solidi (b)

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Interfaces between dissimilar materials are critical to the performance of many electronic devices. In electrical devices where the active transport is through an organic semiconductor (OSC) layer there are metallic electrodes to supply and remove the charge carriers. At metal/molecule and molecule/metal interfaces the electrical contact is usually not Ohmic. As a result, in most metal-organic semiconductors-metal devices charge injection is mainly governed by tunneling across the barriers. When the metal electrodes are ferromagnetic the density of occupied and unoccupied electronic states is spindependent, which presents further subtleties to the electron transfer. In this article we summarize some of the important experimental results that have advanced our understanding of spin-polarized electron transfer across ferromagnetic metal (FM)/OSC interfaces. In particular, we highlight key spectroscopic studies that have revealed insights into the nature of the electronic structure between OSCs and FMs, in particular between Alq 3 and Co and Fe surfaces. We discuss the relationship between energy level diagrams for these systems and transport measurements made on spin-valve devices.

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Alignment of energy levels at theAlq3∕La0.7Sr0.3MnO

Cited by 76 publications

References 40 publications

Ferrodistortive Instability at the (001) Surface of Half-Metallic Manganites

Ferrodistortive Instability at the (001) Surface of Half-Metallic Manganites

Engineering spin propagation across a hybrid organic/inorganic interface using a polar layer

The role of interfaces in organic spin valves revealed through spectroscopic and transport measurements

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