This is a copy of the slides presented at the meeting but not formally written up for the volume.

Recent advances in oxide electronics are indebted to an increased understanding of the material properties at the atomic level. The complex chemical structure of oxides also offers more flexibility: various electronic properties from semiconductors to superconductors and multiferroics, can be tailored by proper materials combinations. The microscopic properties of perovskite oxide interfaces may have a strong impact on the electrical transport properties at and near these interfaces. Recently, the interface between two similar oxide materials, SrTiO3 and LaAlO3, has received much attention since it is suggested to give rise to a two-dimensional electron gas. The polar discontinuity due to different ionic valences of Sr and La can be one possible reason for the interfacial charging. However, other factors like strain in the LaAlO3 film, presence of oxygen vacancies in the SrTiO3 substrate and atomic inter-diffusion may also affect the interface properties. Here we present a detailed experimental investigation of optical, electrical and microstructural properties of heterointerfaces between SrTiO3 and LaAlO3. We found that the interface properties strongly depend on the oxygen pressure conditions during growth of LaAlO3 films. Cathode- and photoluminescence observed from LaAlO3 films grown at 10-6 mbar oxygen pressure was exactly the same as from oxygen reduced SrTiO3 substrates. Additionally, electrical Hall mobility follows the same power-law dependence similar to the one measured in oxygen reduced SrTiO3, suggesting that oxygen vacancies in SrTiO3 can in fact be responsible for the high conductivity at the interface. This is also confirmed on a microscopic level by the findings of local strain fields at the interface reaching 10 nm into the SrTiO3 substrate.

This is a copy of the slides presented at the meeting but not formally written up for the volume.

Recent development of pulsed laser deposition technique makes it possible to build up different kinds of perovskite oxides and to create new electric and magnetic properties of heterointerfaces, which can neither be realized in bulk properties of the constitute oxides and nor be treated as the simple combination of them. The extraction of unique properties of interfaces thus crucially relies on the development of a new method to selectively detect their electronic properties accompanied with magnetism. Here we show a new approach with use of the optical magnetoelectric (ME) effect to address the unique properties of ferromagnetic oxide superlattices (SLs). The ME effect, that is, the control of the polarization P by a magnetic field H or inversely the control of the magnetization M by an electric field E, can be considered as a typical manifestation of cross-correlation phenomena in solids. Even at optical frequencies, such a cross-correlation response coming from the ME effect is known to show up in materials with a lack of both space-inversion and time-reversal symmetries. This is referred to as the optical ME effect. The optical ME response emerges as a change of reflection and transmission when the wavevector k of light is set to parallel or antiparallel to the toroidal moment T defined as P X M, which in turn enables us to control the intensity of light by changing the directions of E and/or H. In this work, we fabricated SLs composed of LaMnO3, SrMnO3, and LaAlO3 and exploited the use of their unique properties of heterointerfaces as a medium for optical ME effect. Such 'tricolor' SLs are expected to artificially break both space-inversion and time-reversal symmetries, which are induced by asymmetric stacking sequences of three different oxides and by the charge-transfer-induced magnetism at LaMnO3/SrMnO3 interfaces, respectively. We patterned the grating structure with a period of 4 ìm on SLs and employed the Bragg diffraction geometry to sensitively detect the optical ME effect. The optical ME effect was clearly observed when the diffracted light was used as a probe. The optical ME response depending on PABC X Minterface is a direct consequence of the symmetry breaking at interfaces. Its magnitude per interface was thus estimated to be tilde operator = varies with = similar to 0.01% in H of 2 kOe, which are relatively large as compared to previously reported values in bulk materials showing the optical ME effect. Our data provide that the present method would be used as a tool for the study of oxide heterointerfaces.

This is a copy of the slides presented at the meeting but not formally written up for the volume.

At heterojunctions between different oxide perovskite phases both lattice and electronic structure is modified by the junction. One interesting question that several groups have studied is just how far into the neighboring materials these perturbations extend. We have studied this for insulating phases as well as conducting phases. For insulating phases it appears that the lattice distortions are healed in a layer about one unit cell thick. By stacking different materials each of which is only a single unit cell thick we have obtained materials that exhibit new properties determined by the stacking architecture. For example, superlattices that lack inversion symmetry have a built-in polarization that is controlled by the direction of the strain asymmetry. For conducting phases, the electronic structure also seems to be modified mainly in a layer only a few unit cells thick. We have studied this in superlattices of SrTiO3 and LaMnO3 in which we vary the thickness of the layers. We use optical conductivity to probe the electronic structure in the near infrared to near ultraviolet spectral region. The conductivity is close to the average of the two constituents, but differs in certain spectral regions, especially for the films with the thinnest supercells.This work was supported by the Department of Energy Basic Energy Sciences program at the Fredrick Seitz Materials Research Laboratory at the University of Illinois, Urbana, IL.

This is a copy of the slides presented at the meeting but not formally written up for the volume.

MBE growth of transition-metal oxide thin films using the pulsed laser deposition (PLD) technique has opened up new opportunities in the electronic structure studies of correlated systems using photoemission spectroscopy [1]. In this talk, I will present the results of photoemission studies on interfaces between a band insulator and a Mott insulator. In SrTiO3/LaTiO3 superlattices [2], metallic states were observed and systematic spectral weight transfer between the coherent part and incoherent part of the Ti 3d band was found to take place [3] as inferred from the electron-energy-loss spectroscopy study [4] and predicted theoretically [5]. For TiO2/VO2 interfaces, on the contrary, no metallic state was observed when VO2 was in the low-temperature insulating phase. The different behaviours are attributed to the absence of polarity discontinuity at the interface:electronic reconstruction;occurs at the polarity-discontinuous SrTiO3/LaTiO3 interface and does not at the polarity-continuous TiO2/VO2 interface. In entirely polar heterostructures LaAlO3/LaTiO3 [6] and LaAlO3/LaVO3 [7], soft x-ray and hard x-ray core-level photoemission measurements revealed that the Ti and V valences change at the topmost layers of the interfaces, suggesting electronic reconstruction competing with chemical reconstruction. This work was done in collaboration with M. Takizawa, H. Wadati, K. Maekawa, A. Chikamatsu, S. Minohara, A. Maniwa, H. Kumigashira, M. Oshima, M. Kawasaki, H. Koinuma, Y. Takata, K. Horiba, M. Matsunami, S. Shin, M. Yabashi, K. Tamasaku, Y. Nishino, D. Miwa, T. Isikawa, K. Shibuya, M. Lippmaa, Y. Nagao, Y. Muraoka, Z. Hiroi, Y. Hotta, T. Susaki, H.Y. Hwang, G.W.J. Hassink, and G. Rijnders. References [1] K. Horiba et al., Rev. Sci. Instr. 74, 3406 (2003). [2] K. Shibuya et al., Jpn. J. Appl. Phys. 43, L1178 (2004). [3] M. Takizawa et al., Phys. Rev. Lett.; 97, 057601 (2006). [4] A. Ohtomo, D.A. Muller, J.L. Grazul and H.Y. Hwang, Nature 419, 378 (2002). [5] S. Okamoto and A.J. Millis, Nature 428, 630 (2004); Phys. Rev. B 70, 241104 (2004). [6] G.W.J. Hassink et al., to be submitted. [7] Y. Hotta et al., submitted to Appl. Phys. Lett.

This is a copy of the slides presented at the meeting but not formally written up for the volume.

Ferromagnetic oxides such as perovskite manganite and spinel ferrite exhibit high magnetic transition temperature and attractive magnetoresistive properties, which make these materials excellent candidates for superior spin electronics devices. The electric field/light controls of magnetisms have been demonstrated in the manganite based heterostructures such as p-n junction and field effect transistor. In addition to 2-D type layered heterostructure, nano-channel (quasi 1-D type) structure is a new strategy to enhance interfacial properties. This structure will be used to prepare planar side-gate field effect devices which control carrier mediated physical properties in isolated nano-sized correlated oxides in a reversible way. Recent studies in manganites have suggested that the ground state of transition metal oxides tends to be inhomogeneous, consisting of ?electric phase separation?; which may bring anomalous responses against external perturbations in nano-scale. Here, the technique of Atomic Force Microscope (AFM) lithography was used to construct robust nano-structures of perovskite manganites down to 30 nm in size. The resulting (La,Ba)MnO3 nano-channel possessed no lithographic damage and exhibited bulk-like room temperature ferromagnetism down to 30 nm beyond electrical phase separation picture [1]. On the contrary, the (La,Pr,Ca)MnO3 nano-channel with 500 nm width exhibited an extremely sharp drop in magnetoresistance against increase of the magnetic field at both 10 K and 50 K, while the 10 μm and the 1 μm channels showed moderate decrease [2]. This result suggests that metallic transition of the single insulating domain, acting as a bottle neck in the channel, leads to digitalized magnetoresistance. As a new candidate for spin oxide hetero/nano-structures, we also report physical properties of ferroelectric gate-ferromagnetic FET structure using tunable ferromagnetic semiconductor of Fe3-x MxOx (M=Mn, Zn) [3, 4] and Fe3-x MnxOx nano-channel structure prepared by Mo nano-mask AFM lithography technique [5].

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Stripe domains in ferroelectric thin films form in order to minimize the total energy of the film. It has been known for some time that a stable configuration is reached when the decrease in elastic energy from domain formation is balanced by the energetic costs of domain wall formation, local elastic strains in the substrate, and internal electric field formation from domain polarizations. The size and strain of each domain is determined by the lattice mismatch and the energetic costs of interface formation. Recent piezoelectric force microscopy measurements have shown that BiFeO3 (BFO) films on SrRuO3/SrTiO3 (001) substrates form striped polarization domains. Since the details of the local structure and polarization cannot be measured at the same time with conventional techniques, we have used synchrotron x-ray microdiffraction to study these effects. Probing only a few domains at a time with the submicron x-ray spot resulted in a diffraction pattern near the substrate (103) reflection consisting of several BFO peaks. We have unambiguously assigned these peaks to individual structural variants. Based on these results, we propose a physical model that includes the striped domains. The structural variants within the stripes are similar to those predicted by striped patterns in rhombohedral films which minimize elastic energy. The local piezoelectric properties were measured using time-resolved microdiffraction in order to examine the role of the striped domains in the linear responses of the film. The out of plane piezoelectric coefficient d33 was approximately 50 pm/V and the piezoelectric strain was proportional to electric field was up to 0.55%, the maximum strain we have measured. The projection of the in-plane piezoelectric coefficients onto the reciprocal space maps for different structural variants had vastly different values due to the differences in orientation of the domains.

This is a copy of the slides presented at the meeting but not formally written up for the volume.

We have made very thin films of LaAlO3 on TiO2 terminated SrTiO3 and have measured the properties of the resulting interface in various ways. We have made very thin films of LaAlO3 on TiO2 terminated SrTiO3 and have measured the properties of the resulting interface in various ways. Transport measurements show a sheet carrier density of 1016 cm-2 and a mobility around 104 cm2 V-1 s-1. In situ UPS results indicate that oxygen vacancies play an important role in the creation of the charge carriers and that these vacancies are introduced by the pulsed laser deposition process used to make the hetero-interfaces [1]. Our results explain for the first time [2] the origin of the large sheet carrier densities and high mobility observed previously. XAS and spectroscopic ellipsometry [3] measurements confirm the existence of (oxygen) defects in the SrTiO3 and their variation with the oxygen pressure during deposition. Simple model calculations confirm the plausibility of having defects at the origin of charge carriers while still maintaining a high mobility [4]. By means of annealing experiments in atomic oxygen we try to answer the question whether an intrinsically doped interface does indeed exist at lower carrier concentrations [2]. Due to its reactive nature (i.e., binding energy in an oxygen molecule is about 5 eV), atomic oxygen will have much more power to eliminate any oxygen vacancies compared to conventional annealing methods. [1] W. Siemons et al, CondMat/0603598 [2] W. Siemons, G. Koster, H. Yamamoto, W. A. Harrison, T. H. Geballe, G. Lucovsky, D.H.A. Blank and M.R. Beasley, in preparation [3] G. Lucovsky, H. Seo and J. Luning, unpublished [4] G. Koster and W. Harrison, in preparation.

This is a copy of the slides presented at the meeting but not formally written up for the volume.

The interface electronic structure of transition metal oxides has attracted considerable attention in recent years. Given the versatile physical properties of these materials, and the interest in developing novel functional devices unattainable by conventional semiconductors, understanding interface barrier formation and control is a central issue. Among various interface structures, single interface junctions are the simplest structure for their study, and their transport properties can provide much of the essential information for depiction of the interface electronic structure. Recently, magnetic field dependent current-voltage (I-V) and capacitance-voltage (C-V) characteristics were reported for a junction between oxygen deficient manganite (La0.7Sr0.3MnO3-ä) and 0.01wt% Nb doped SrTiO3 (Nb:STO). By contrast, no magnetic field dependence was observed for the stoichiometric junction (La0.7Sr0.3MnO3 / Nb:STO) [1]. La0.7Sr0.3MnO3-ä is a ferromagnetic metal with a Curie temperature lower than the stoichiometric counterpart, and Nb:STO is an n-type band semiconductor. The magnetic field dependence of the I-V and C-V are contrary to the expectation from the Zeeman effect [1]. To elucidate the origin of the magnetic field dependence observed, we used internal photoemission (IPE) to directly probe the evolution of the Schottky barrier height. In this technique, the reverse junction current is monitored while the sample is illuminated with monochromatic light of varying wavelength. IPE is a direct, reliable method for the determination of Schottky barrier heights since the measurement is free from external electric field, eliminating any complexity associated with bias dependent effects observed in the case of I-V and C-V. In addition, its compatibility with external magnetic field makes this method especially desirable for investigating interface electronic structures involving magnetically sensitive materials. Junctions with different oxygen stoichiometry were grown by pulsed laser deposition of a La0.7Sr0.3MnO3 target on Nb:STO substrates, and their I-V, C-V and IPE characteristics were measured under magnetic field. Magnetic field dependence was observed by all three techniques for La0.7Sr0.3MnO3-ä / Nb:STO, whereas they were field independent for La0.7Sr0.3MnO3 / Nb:STO. In La0.7Sr0.3MnO3-δ / Nb:STO, the barrier height determined from IPE measurements significantly decreased with magnetic field, which is consistent with the I-V and C-V results. The origin of the magnetic field dependent Schottky barrier height will be discussed. [1] N. Nakagawa et al., App. Phys. Lett. 87, 241919 (2005).

This is a copy of the slides presented at the meeting but not formally written up for the volume.

We present a high-resolution transmission electron microscopy study, on the unit-cell scale, of the degree of tetragonality and the displacements of cations away from the centrosymmetry positions in an ultra-thin epitaxial PbZr0.2Ti0.8O3 film on a SrRuO3 electrode layer deposited on a SrTiO3 substrate. TEM results show that the lattice is highly tetragonal at the centre of the film with a c/a ratio of about 1.08, while it shows a reduced degree of tetragonality in the regions close to the interfaces. Most strikingly, we find that the maximum off-centre displacements for the central area of the film do not scale with the tetragonality in comparison with the bulk materials. The calculated switched polarization from the measured cationic displacement is 80 ìC/cm2 , and thus only half of the nominal bulk value. It is in very good agreement with electrical measurements of the switched polarization obtained via the PUND method. Furthermore, a systematic reduction of the atomic displacements is measured at the interfaces. This suggests that interface-induced suppression of the ferroelectric polarization plays a critical role in the size effect of nanoscale ferroelectrics. These issues will be discussed further in this presentation. This work was partially supported by the National Science Foundation (NSF) under Grants DMR-0132918, NSF-MRSEC DMR-0080008, and an NSF US-Europe program DMR-0244288. V.N also acknowledges the support of the Alexander von Humboldt Foundation for his stay in Germany and the financial support of an Australian Research Council Discovery Grant 0666231.

This is a copy of the slides presented at the meeting but not formally written up for the volume.

Research into new concepts for oxide-electronic devices has been enriched by the emerging field of functional interfaces. A high control of the materials down to the atomic level enables the improvement of existing oxide devices, like magnetic tunnel junctions, but also the formation of new artificial interface phases. Previous work revealed the existence of a metallic electron gas at the interface between the two band-insulators, LaAlO3 and SrTiO3, for a certain atomic arrangement [1,2]. Several studies on single epitaxial connections between LaAlO3 and SrTiO3 have revealed them to be either high-mobility electron conductors or insulating, depending on the atomic stacking sequences. An important point to take into account is the formation of oxygen vacancies for low deposition pressures (<10-5 mbar). For this growth regime the transport properties are fully dominated by the presence of the oxygen vacancies. In this talk we will show a detailed investigation of the controllable electronic properties of coupled interfaces in SrTiO3-LaAlO3-SrTiO3 heterostructures. Recently we reported a critical separation distance of 6 perovskite unit cell layers (~23 Å) for the electronic coupling of closely-spaced complementary interfaces in SrTiO3/LaAlO3 multilayer structures [3]. We showed that a decrease of the interface conductivity and carrier density occurs when the LaO:TiO2 and AlO2:SrO interfaces are brought closer together. Interestingly, the high carrier mobilities characterizing the separate conducting interfaces were found to be maintained in such coupled structures down to sub-nanometer interface spacing. Here, we will explain in more detail the electronic properties of the closely spaced LaO:TiO2 and AlO2:SrO interfaces below the critical separation distance. The carrier density at room temperature for dLAO5 is similar to a single LaO:TiO2 interface and has a value of ~1.5X1014 cm-2, corresponding to ~0.23 electrons per unit cell area on the LaO:TiO2 interface. In this, the contribution by the AlO2:SrO interface to the sheet carrier density is neglected, due to its much lower conductivity. When both interfaces are brought closer to each other the electronic coupling between them is increased and the charge density at room temperature is reduced to 0.15, 0.11 and 0.07 electrons per unit cell area for a spacing of respectively 3, 2 and 1 unit cells. However, for lower temperatures the sheet carrier density decreases and becomes constant for all coupled heterostructures at temperatures below 10 K. This constant low temperature carrier density has a value of 2.0×1013 cm-2 and corresponds to 0.003 electrons per unit cell area. These results show the ability to control the electronic properties in SrTiO3 heterostructures and to vary the carrier density homogeneously over the interface.

This is a copy of the slides presented at the meeting but not formally written up for the volume.

Recent experiments by Matsushita et al(1) lead to the conclusion that the superconductivity found in semiconducting PbTe doped with Tl ions of a few times 10/20 per cc (the solubility limit) is caused by an excitonic mechanism. They find 1) the superconducting properties are fit by weak-coupled BCS (mean-field) theory 2) the Tcs as a function of doping are roughly two orders of magnitude higher than comparably doped chalcogen semiconductors and an order of magnitude higher than electron-doped SrTiO3 3)No superconductivity is found upon doping in the same concentration range with cations other than Tl. The above facts virtually eliminate the possibility that the superconductivity might be due to local phonon modes to the many valley structure of the valence band. The further findings of Matsushita et al(2) show that the observed low temperature resistance minima are fit by a charge-Kondo mode assuming a near degeneracy of the +1 and +3 Tl ionic states(the +2 state of Tl is at much higher energy as evident from the chemistry of Tl ). The assumption is justified by measurements of the Hall number. The exitonic pairing mechanism is thus simply the exchange of paired electrons between two Tl valence states and the PbTe valence band. Empirical evidence strongly suggests that the TlO charge reservoir layers in Tl high Tc cuprates, and likewise HgO and BiO layers in their respective cuprates are responsible for large enhancements in Tc presumably by exchanging pairs of carriers with the CuO2 layers.1. Y. Matsushita, H. Bluhm, T.H. Geballe, and I.R. Fisher, Phys. Rev. Lett. 94, 157002 (2005).2. Submitted.

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The growth of heterostructures combining oxide materials is a new strategy to design novel artificial multifunctional materials with interesting behaviors ruled by the interface. There has been increasing interest in heterostructures combining oxides with different functionalities and ground states competing at the interface. In structures involving oxides, interfaces are especially complex and various factors like interface disorder and roughness, epitaxial strain, polarity mismatch etc., are responsible for modified properties at the interface over nanometer length scales. In this presentation we will focus on cuprate / manganite heterostructures made of YBa2Cu3O7 (YBCO) and La1-xCaxMnO3 (LCMO), where the Ca content is varied over a wide range. The manganite grows epitaxially on the superconductor with different degrees of strain depending on the Ca content. For x=0.3 the manganite is ferromagnetic what causes a strong depression of the superconducting order parameter at the YBCO side. Interestingly, there is also a depression of the ferromagnetic moment at the interface suggesting charge transfer (electrons) from the manganite into the YBCO. This is confirmed growing superlattices combining YBCO with the parent manganite compound with x=0, which is nominally an AF insulator. Actually, for LMO thickness below 6 unit cells (2,4 nm) the layers are non magnetic and insulating as expected. However, above this LMO thickness (6 unit cells) we show that superconductivity is strongly suppressed and ferromagnetism is induced at the interface providing a strong evidence for the charge transfer scenario. The control of layer bulk doping by charge transfer at the interface opens new possibilities of tailoring the electronic states at the interface for the design of novel functionalities and devices. Work supported by CICYT MAT2005 06024 C02-02 and DOE.

This is a copy of the slides presented at the meeting but not formally written up for the volume.

Description: Semiconductor physics contains a rich body of theory and working designs. However, their material properties seem to be reaching their limits. Perovskite oxides on the other hand have abundant physical properties, but are still under active investigation. The advent of RHEED-monitoring of pulsed laser deposition allows for the fabrication of structures with single unit cell (4 Å) thick layers. In this way we may be able to fabricate quantum well structures for both applications and fundamental investigations. Superlattices of the Mott insulator LaTiO3 (LTO) and the band gap insulator SrTiO3 (STO) form such a structure. The superlattices are metallic, both as-grown and post-annealed [1]. This has been attributed to the existence of metallic states at the interfaces between LTO and STO [2]. At these interfaces the electron density is found to extend about 10 Å into the STO. However, theoretically, the required length scale for quantum confinement is of the order of 4 Å. A possible way to increase this confinement is to use a buffer material with a larger band gap than that of LTO (similar to semiconductor band gap engineering) and/or with a lower dielectric constant [2]. LaAlO3 (LAO) is such a material (ΔELAO = 5.6 eV vs. ΔESTO = 3.2 eV, εLAO = 24 vs. εSTO = 300). Here we report on the growth of LTO/LAO superlattices on STO substrates. As-grown superlattices of LTO/LAO are metallic, while post-annealing turns them insulating. This may be explained from a disorder-order transition in a 2D Mott-Hubbard model [3]. XPS and EELS measurements of the titanium valence show interesting differences for LTO layers close to and far away from the sample surface. The former, for thin LAO capping layers, show the presence of Ti4+ while the latter only have Ti3+. Hard XPS of samples with varying capping layer thickness shows an exponential dependence of the Ti3+ contents on a length scale of about 5 unit cells. [1] A. Ohtomo et al., Nature 419, 378-380 (2002). [2] S. Okamoto & A.J. Millis, Phys. Rev. B 70, 075101 (2004). [3] D. Heidarian & N. Trivedi, Phys. Rev. Lett. 93, 126401 (2004).

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In this talk, the focus will be on recent experiments performed on superconducting doped SrTiO3 films using the ferroelectric field effect. Using thin single crystal films of Nb-doped SrTiO3, we have used the polarization field of ferroelectric Pb(Zr,Ti)O3 to electrostatically tune the electronic properties of Nb-doped SrTiO3. Atomic force microscopy was used to locally reverse the ferroelectric polarization, inducing large resistivity and carrier modulations, resulting in a clear shift in the superconducting critical temperature [1]. By poling sub-micron scale domains, the carrier density and the electronic properties of the superconducting channel were locally modified. Transport measurements reveal a steplike behavior in the current-voltage and resistance-magnetic field characteristics. This behavior, not observed in homogeneously poled samples, is ascribed to phase slip lines which are more easily generated in inhomogeneous superconductors. More generally, the technique developed should allow Josephson junctions, SQUIDS and superconducting circuits to be directly written in a Nb-doped SrTiO3 film using atomic force microscopy, an idea proposed in 1997 by C.H. Ahn et al. [2]. [1] K. Takahashi, D. Jaccard, M. Gabay, K. Shibuya, T. Ohnishi, M. Lippmaa, J.-M. Triscone, Nature 441,195 (2006). [2] C.H. Ahn, T. Tybell, L. Antognazza, K. Char, R.H. Hammond, M.R. Beasley, Ø. Fischer, and J.-M. Triscone. Science 276, 1100 (1997).

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Description: Inhomogeneous dynamical mean-field theory is developed to determine electronic charge reconstruction for strongly correlated multilayered nanosctructures. The theory is applied to the problem of charge and heat transport perpendicular to the layers. We find that the electronic charge reconstruction can significantly enhance the thermal transport properties producing Seebeck coefficients larger than 160 microvolts/K and figure-of-merits larger than 1. This work shows that at the nanoscale, properties of materials can be modified so much near the interfaces, that they no longer resemble their bulk constituents, and novel behavior can arise which may have important technological implications for devices.

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The physical properties of complex oxides are characterized by the interplay of charge-,spin-,orbital and lattice degrees of freedom. Combining oxides with different spin-,charge- or orbital order opens generate an additional degree of freedom that can give rise to novel physical phenomena. We have studied the interface of the system La0.67.Ca.33MnO3 and YBa2Cu3O7 prepared by conventional PLD as an example representing the combination of ferromagnetic and superconducting oxides by a variety of techniques including neutron diffraction and XMCD analysis. It turns out that at the interface interaction effects are taking place at two different length scales. One is based on the self ? injection of spin-polarized quasiparticles with a length scale of ~ 10nm, the other is a short range exchange interaction with a length scale of ~ 3 nm. The short range interaction gives rise to an antiferromagnetic coupling of the Mn and Cu spins across the interface. The results are discussed in the frame of orbital interactions across the interface. Furthermore, it could be shown that in FM/SC/FM trilayer systems a so far unknown coupling of adjacent magnetic layers occurs when the superlattices are cooled through the superconducting transition temperature. It is well established that two ferromagnetic layers are coupled through an intervening metallic layer by the Ruddermann-Kittel-Kasuya-Yoshida (RKKY) mechanism. The sign of the coupling oscillates from positive to negative with the thickness of the metallic layer. On the other hand, the interaction between ferromagnetic (FM) and superconducting (SC) layers in a FM/SC/FM heterostructure is not well understood. Tentatively, we propose a coupling mechanism mediated by London screening currents to explain our observations.