aoi

Advanced Optical Imaging

We also make use of the interaction of polarized light with magnetically and electrically ordered matter for high-resolution optical imaging of domains. We are developing an infrastructure for advanced optical characterization based on confocal microscopy with the focus on complex domain imaging with sub-micrometer resolution of magnetoelectric systems.

magnetophotonic

Magnetophotonic and Magnetoplasmonic Materials

We exploit the interaction of light with matter to obtain tailored spectral photonic responses. One strategy is based on 2D and 3D composite complex materials –photonic crystals– in which the matter is structured at the scale of the visible of near-infrared wavelengths. In this case, a photonic band structure emerges in which the optical responses dramatically increase at light wavelengths defined by the geometry. On the other hand, we exploit plasmon responses at metal/dielectric interfaces to obtain enhanced optical properties at specific frequencies. We thus combine magnetic materials with either photonic crystals or plasmon resonators to produce systems with customized magneto-optic spectral responses.

 Selection of our recent publications:

 

 

fos

Functional oxides on Silicon

Silicon is the most fundamental technological material for electronics. At the same time, oxides display a remarkably variety of functional properties, including ferroelectricity or magnetism. Thus, a successful coupling of functional oxides with silicon has an enormous potential for new applications in electronics. A serious challenge issue is to match the dissimilar (structurally, thermally, and in general chemically reactive) oxides and silicon in hybrid structures. We have recently initiated the research on the integration of functional oxides on silicon, with focus on ferroelectric and magnetic oxides. For that purpose, we exploit atomic growth control with in-situ RHEED monitoring, as well as advanced microstructural (TEM) and functional (magnetic, magneto-optic, ferroelectric) characterization. Specific objectives in progress include integration of i) ultrathin (a few nanometer thick) ferroelectric perovskites and ferrimagnetic spinels on silicon, and ii) ferroelectric perovskites on silicon membranes.

 


Domain matching epitaxy of ferrimagnetic CoFe2O4 thin films on Sc2O3/Si(111)
Applied Physics Letters 99, 211910 (2011)
http://apl.aip.org/resource/1/applab/v99/i21/p211910_s1


CoFe2O4/buffer layer ultrathin heterostructures on Si(001)
Journal of Applied Physics 110, 086102 (RC) (2011)
http://jap.aip.org/resource/1/japiau/v110/i8/p086102_s1


Flat epitaxial ferromagnetic CoFe2O4 films on buffered Si(001)
Thin Solid Films 519, 5726 (2011)
http://www.sciencedirect.com/science/article/pii/S0040609010018663 


 

image003

Multiferroics and Magnetoelectric Systems

The cross-coupling between magnetism and ferroelectricity affords very promising avenues for the development of novel electronic devices. The feasibility of electrical control of the magnetization and viceversa, the control of the electrical polarization with magnetic fields, is the basic step towards new memories with multi-bit storage capabilities (in which the information is encoded by the magnetization and polarization states) or to dissipation-less operation of magnetic memories. We investigate both single-phase multiferroics as well as composite magnetoelectric materials in which magnetic and ferroelectric phases are coupled, either in 3D nanocomposites or 2D thin film structures. Our methodology is based on the study of magnetoelectric coupling exploiting advanced ferroelectric characterization under magnetic fields as well as magnetometry and magneto-optic imaging under electric fields.

 Selection of our recent publications:

  • Strain tuned magnetoelectric coupling in orthorhombic YMnO3 thin films. Appl. Phys. Lett. 95, 142903 (2009).
  • Electric-field control of exchange bias in multiferroic epitaxial heterostructures. Phys. Rev. Lett. 97, 227201 (2006).

 

image001

Magnetic Oxide Thin Films

Spin dependent electron transport in magnetic materials is the basic physical mechanism for spintronics. For the integration in spintronics devices, magnetic materials have to be structured at the nanoscale, either as thin films or in nanostructures. It is important, therefore, to have a complete understanding of the physical properties of magnetic structures at such small scales. Our focus is at the investigation of the properties like magnetization, spin polarization, or conductivity for nanometric thin films and nanostructures. Our methodology, in addition to conventional magnetotransport characterization, includes also conductive atomic force microscopy as well as magneto-optics to analyze electronic transport at optical frequencies.

Selection of our recent publications:

  • Nontunnel transport through CoFe2O4 nanometric barriers. Appl. Phys. Lett. 97, 242508 (2010)
esr

Electronic/Structural Reconstructions at Oxide Surfaces and Interfaces

The physical properties of bulk materials, e.g., magnetism or electronic transport, may be dramatically modified at their surfaces or at the interfaces with other materials. In particular, oxides offer an ideal platform to analyze such phenomena related to the effects of charge transfer, strain or chemical segregation on nanoscale regions –typically a few unit cells around interfaces and surfaces–. A particular spectacular example is the high mobility transport found at the interface of two oxide band insulators, LaAlO3 and SrTiO3, which may be the gateway to novel emergent oxide electronics. Our goal is to understand the physics behind the phenomena appearing within these nanometric regions for eventual new applications and devices. By using a variety of single crystals as structural templates, we grow oxide thin layers –usually a few nanometers thick– with tools that allow the growth with atomic control precision. Our multidisciplinary approach includes a range of sophisticated experimental methodologies, including pulsed laser deposition with in-situ RHEED, advanced magnetic, dielectric and magneto optic characterization, Atomic Force Microscopy, NMR, STEM-EELS, and X-Ray Synchrotron Radiation.

Selection of our recent publications: