Research Groups

RESEARCH UNIT: Advanced Structural and Functional Characterization

Crystallography of Magnetic and Electronic Oxides and Surfaces (CMEOS)

Symmetry motivated approaches anticipate the identification on new improper magnetoelectric multiferroics from both polar and nonpolar magnetic distortions.

The activities of the Crystallography of Magnetic and Electronic Oxides and Surfaces (CMEOS) group are based on the application of chemical and magnetic crystallography methods to the investigation of emergent functional oxides. Combining an intensive use of Large Scale Facilities (such as neutron and synchrotron sources) with symmetry analysis methodologies, we investigate the symmetry-properties relationship associated to structural, magnetic or electronic orders in functional oxides.

Current research lines include the study of structure-properties relationship in new magnetic, multiferroic and magnetoelectric materials with special charge, spin or electronic orders, and the study of novel oxides with giant responses for information technologies. In addition to bulk materials and films, surface diffraction synchrotron techniques and surface characterization methods are applied to the study of ordering related phenomena in low-dim systems and interfaces.

Members

  • Prof. José Luis García-Muñoz - Research Professor
  • Dr. Xavier Torrelles - Research Scientist
  • Dr. Javier Herrero Martín - ALBA Scientist
  • Prof. Vassil Skumryev - ICREA Research Professor-UAB
  • Xiaodong Zhang - PhD Researcher
  • Arnau Romaguera - PhD Researcher
  • Adrián Crespo - PhD Researcher

A: Polar/Nonpolar transitions in Tb2MnNiO6, ε-Fe2O3 and NaPrFeWO6 potential multiferroics. B: Evolution of the FE spiral magnetic phase in YBaCuFe1-xMxO5. Single-crystals and magnetic Laue pattern. C: (a) optimum TiO2(011)-(2x1) geometry and (b) ideal bulk terminated TiO2(011) structure. Inset: evolution of the rutile(011) surface  from its ideal surface to the hydroxylated (1x1) surface.

Achievements

Our activities focused on polar magnetic materials, multiferroics, chiral magnetism and photocatalytic oxide surfaces among others. Distinct families of novel and potential improper multiferroics presenting frustration were fabricated in polycrystalline, single-crystal or film forms. Distinct nonpolar/polar transitions were identified and described as a function of temperature, chemical and hydrostatic pressure or external fields in FM and AFM oxide families such as NaLnFeWO6, Tb2MnMO6, ε-Fe2O3 or ε-(Fe1-xMx)2O3 unveiling the relevant magnetic and structural distortion modes switching at the transitions. A different strategy focused on single-crystal and powder samples studies of incommensurate magnetic phases (ferroelectric and non-ferroelectric) in low and high-temperature multiferroics. Noncollinear and chiral magnetic orders provide excellent opportunities for the electric control of magnetism thanks to the coupling between electron spin and its orbital motion. Samples were fabricated with a stable chiral (spiral) magnetic phase up to 360 K.

One of the most interesting systems for photovoltaic conversion of light to electricity is Titania. Rutile polymorph absorbs significant amounts of light only in the UV portion of the spectrum, however, most studies don’t focus on the direct interaction between electrolyte/H2O at the interface with the catalyst but on the characterization and its efficiency. Efficiency optimisation of photocatalysts not only depends on their intrinsic design but also in the knowledge of the real processes happening at their interfaces before arriving to the final specimens. Understanding the interaction of water on solid surfaces is of both fundamental and practical interest. Rutile(011) surface (considered as a model oxide surface) shows a reversible (2x1) reconstruction in UHV conditions that evolves into a structure (1x1) in the presence of water and vice versa. This phase transformation is due to the presence of hydroxyls at the TiO2(011) interface.

Publications

Magnetic inversion symmetry breaking and spin reorientation in Tb2MnNiO6 : a polar strong ferromagnet
Jose Luis García-Muñoz, Javier Blasco,  Xiaodong Zhang and Oscar Fabelo
Phys. Rev. B 99, 184444 [9pp], 2019

Spin ordering and physical properties of NaPrFeWO6 and NaSmFeWO6 with polar double perovskite structure
Javier Blasco, José A Rodríguez-Velamazán, Gloria Subías, José Luis García-Muñoz, Jolanta Stankiewicz and Joaquín García
Acta Materialia  176, 53-62, [10pp], 2019

Double-cell superstructure and vacancy ordering in tensile-strained metallic thin films of Pr0.50Ca0.50CoO3 on LaAlO3
Jessica Padilla-Pantoja,  Xavier Torrelles, Jaume Gazquez, Juan Rubio-Zuazo, Javier Blasco, Javier Herrero-Martín and Jose Luis García-Muñoz
Phys. Rev. Materials 3, 104407 [9pp], 2019

Epitaxial growth and structure of cobalt ferrite thin films with large inversion parameter on Ag(001)
Maurizio De Santis, Aude Bailly, Ian Coates, Stéphane Grenier, Olivier Heckmann, Karol Hricovini, Yves Joly, Veronique Langlais, Aline Y. Ramos, Christine Richter, Xavier Torrelles, Stéphanie Garaudé, Olivier Geaymond and Olivier Ulrich
Acta Cryst.,. B75, 8–17, 2019

Electronic and structural reconstructions of the polar (111) SrTiO3 surface
X. Torrelles, G. Cantele, G. M. De Luca, R. Di Capua, J. Drnec, R. Felici, D. Ninno, G. Herranz, and M. Salluzzo
Phys. Rev. B 99, 205421, 2019

Water-Induced Reversal of the TiO2(011)-(2 x 1) Surface Reconstruction: Observed with in Situ Surface X-ray Diffractions
H. Hussain, M.H.M. Ahmed, X. Torrelles, D. C. Grinter, G. Cabailh, O. Bikondoa, C. Nicklin, U. Aschauer, R. Lindsay and G. Thornton
J. Phys. Chem. C, 123, 13545−13550, 2019

Structure of a Superhydrophilic Surface: Wet Chemically Prepared Rutile-TiO2(110)(1 x 1)
J. P.W. Treacy, H. Hussain, X. Torrelles, G. Cabailh, O. Bikondoa, C. Nicklin, G. Thornton, and R. Lindsay
J. Phys. Chem. C 123, 8463−8468, 2019

Pristine and hydrated fluoroapatite (0001)
Xavier Torrelles, Immad M. Nadeem, Anna Kupka, Adrián Crespo-Villanueva, Sandrina Meis, Hermann Gies and Oier Bikondoa
Acta Cryst., B75, 830–838, 2019

Awards and Recognitions

  • J.L. Garcia-Muñoz, elected member of the Scientific Panel of the ALBA-Synchrotron Light Source: Chemistry & Materials Science Panel
  • J.L. Garcia-Muñoz, National representative of the Spanish Association of Synchrotron Users in the European Synchrotron and FEL User Organisation (ESUO).
Coordination
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