October 2011 Volume 10, Issue 10

Editorial

Not a clear cut p723
doi:10.1038/nmat3140
Facing budget cuts, the UK's research councils are forced to make unpopular choices. Effective consultations should guide decisions.
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Research Highlights

Curly contacts | Heat at the borders | As sensitive as human skin | Hydrogen on the spot | Replication and reproduction

News and Views

Letters

Evolution and control of oxygen order in a cuprate superconductor pp733 - 736
Nicola Poccia, Michela Fratini, Alessandro Ricci, Gaetano Campi, Luisa Barba, Alessandra Vittorini-Orgeas, Ginestra Bianconi, Gabriel Aeppli and Antonio Bianconi
doi:10.1038/nmat3088
The arrangement of defects in solid-state phases has an enormous influence on material properties. It is here shown that powerful X-rays can be used to change the properties of an oxide superconductor, thus effectively writing superconducting regions within an insulating matrix. The results open the way to the manipulation of superconductors and potentially other phases.
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See also: News and Views by Littlewood

Long-range spin Seebeck effect and acoustic spin pumping pp737 - 741
K. Uchida, H. Adachi, T. An, T. Ota, M. Toda, B. Hillebrands, S. Maekawa and E. Saitoh
doi:10.1038/nmat3099
The coupling between electron spins and phonons could lead to a new typology of electronic devices. The effects of such coupling are now experimentally demonstrated by injecting sound waves into a magnetic strip. The results also help to explain the origin of the spin Seebeck effect, which has been controversial for a while.
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Seebeck effect in magnetic tunnel junctions pp742 - 746
Marvin Walter, Jakob Walowski, Vladyslav Zbarsky, Markus Münzenberg, Markus Schäfers, Daniel Ebke, Günter Reiss, Andy Thomas, Patrick Peretzki, Michael Seibt, Jagadeesh S. Moodera, Michael Czerner, Michael Bachmann and Christian Heiliger
doi:10.1038/nmat3076
The combined magnetic and thermoelectric properties of nanostructures have recently attracted considerable attention. It is now demonstrated that the Seebeck coefficient in a magnetic tunnelling junction is strongly dependent on the magnetic configuration.
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Programming magnetic anisotropy in polymeric microactuators pp747 - 752
Jiyun Kim, Su Eun Chung, Sung-Eun Choi, Howon Lee, Junhoi Kim and Sunghoon Kwon
doi:10.1038/nmat3090
Superparamagnetic nanoparticles under an external magnetic field align in the field’s direction to minimize magnetic-dipole interactions. By modulating and fixing the alignment of magnetic nanoparticles in polymeric microcomponents through photopolymerization, magnetic nanocomposite microactuators were programmed to undergo complex motion, such as anisotropic bending and crawling.
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Articles

Interface-induced room-temperature multiferroicity in BaTiO₃  pp753 - 758
S. Valencia, A. Crassous, L. Bocher, V. Garcia, X. Moya, R. O. Cherifi, C. Deranlot, K. Bouzehouane, S. Fusil, A. Zobelli, A. Gloter, N. D. Mathur, A. Gaupp, R. Abrudan, F. Radu, A. Barthélémy and M. Bibes
doi:10.1038/nmat3098
With only a few known useful room-temperature multiferroics, other ways of achieving materials showing magnetism as well as electrical polarization are sought. The discovery that the ferroelectric BaTiO₃ also shows magnetism at room temperature at the interface with iron or cobalt marks a new approach to achieving multiferroic properties.
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Probing bulk electronic structure with hard X-ray angle-resolved photoemission pp759 - 764
A. X. Gray, C. Papp, S. Ueda, B. Balke, Y. Yamashita, L. Plucinski, J. Minár, J. Braun, E. R. Ylvisaker, C. M. Schneider, W. E. Pickett, H. Ebert, K. Kobayashi and C. S. Fadley
doi:10.1038/nmat3089
Angle-resolved photoemission spectroscopy is possibly the most widely used technique to probe the electronic structure of crystals. Unfortunately the technique is usually too sensitive to surface properties. It is now demonstrated that by using hard X-rays as the incident radiation it is possible to probe the electronic structure in the bulk.
Abstract | Full Text | PDF
See also: News and Views by Feng

Colloidal-quantum-dot photovoltaics using atomic-ligand passivation pp765 - 771
Jiang Tang, Kyle W. Kemp, Sjoerd Hoogland, Kwang S. Jeong, Huan Liu, Larissa Levina, Melissa Furukawa, Xihua Wang, Ratan Debnath, Dongkyu Cha, Kang Wei Chou, Armin Fischer, Aram Amassian, John B. Asbury and Edward H. Sargent
doi:10.1038/nmat3118
Organic ligands enhance the stability and the solution processability of semiconductor quantum dots, but they can impede charge transport in films of such nanoparticles. Passivation with atomic ligands now offers an alternative strategy that enables the fabrication of PbS colloidal-quantum-dot solar cells with power-conversion efficiencies of up to 6%.
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A 3.90 V iron-based fluorosulphate material for lithium-ion batteries crystallizing in the triplite structure pp772 - 779
P. Barpanda, M. Ati, B. C. Melot, G. Rousse, J-N. Chotard, M-L. Doublet, M. T. Sougrati, S. A. Corr, J-C. Jumas and J-M. Tarascon
doi:10.1038/nmat3093
Increasing the energy density of lithium-ion batteries is crucial for consumer electronics and electric-vehicle applications. A polyanionic material that crystallizes in the triplite structure by substituting 5at.% of Mn for Fe in a fluorosulphate material now exhibits an enhanced potential of 3.90 V for the Fe²⁺/Fe³⁺ redox couple.
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Co₃O₄ nanocrystals on graphene as a synergistic catalyst for oxygen reduction reaction pp780 - 786
Yongye Liang, Yanguang Li, Hailiang Wang, Jigang Zhou, Jian Wang, Tom Regier and Hongjie Dai
doi:10.1038/nmat3087
Developing oxygen-electrode catalysts with high activity at low cost for renewable energy applications such as water splitting and fuel cells is challenging. A hybrid material of Co₃O₄ nanocrystals grown on reduced graphene oxide exhibits enhanced catalytic performance for the oxygen reduction and oxygen evolution reactions.
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Gas detection by structural variations of fluorescent guest molecules in a flexible porous coordination polymer pp787 - 793
Nobuhiro Yanai, Koji Kitayama, Yuh Hijikata, Hiroshi Sato, Ryotaro Matsuda, Yoshiki Kubota, Masaki Takata, Motohiro Mizuno, Takashi Uemura and Susumu Kitagawa
doi:10.1038/nmat3104
Methodologies capable of directly visualizing and detecting gases are important for a wide variety of applications that involve instantaneous decision-making in complex environments and locations. A strategy for the capture and detection of gases by co-operative structural transformations of a flexible porous coordination polymer and fluorescent reporter molecules is now reported.
Abstract | Full Text | PDF

Large variation of vacancy formation energies in the surface of crystalline ice pp794 - 798
M. Watkins, D. Pan, E. G. Wang, A. Michaelides, J. VandeVondele and B. Slater
doi:10.1038/nmat3096
First-principles calculations show that water molecules at the surface of crystalline ice have high variability in their binding energies. Such an amorphous character of a crystalline surface is unusual, and for ice it is a result of electrostatic frustration and the relaxation of geometric constraints. The findings have consequences for ice catalysis, surface pre-melting and growth.
Abstract | Full Text | PDF
See also: News and Views by Ojamäe

Spatially controlled simultaneous patterning of multiple growth factors in three-dimensional hydrogels pp799 - 806
Ryan G. Wylie, Shoeb Ahsan, Yukie Aizawa, Karen L. Maxwell, Cindi M. Morshead and Molly S. Shoichet
doi:10.1038/nmat3101
Bioactive proteins within hydrogel scaffolds used to culture cells can guide cellular activities, but the control of the location of the proteins has proved difficult. Using the multiphoton laser of a confocal microscope, simultaneous patterning of two growth factors, which remain bioactive after immobilization, is now shown in three-dimensional hydrogels. The technique should be applicable to the patterning of a variety of proteins.
Abstract | Full Text | PDF
See also: News and Views by West