The direct action on the magnetization of a nanostructure by a spin-polarized electrical current is presently the subject of much study. This effect rests on the spin polarization of the electrical current in ferromagnets. In this talk, I will describe the special case where the structure is a nanowire that contains a magnetic domain wall, the current leading to domain wall motion.

Both the experimental aspect and the micromagnetic modeling of this effect will be presented.

Graphene has been considered by many as a revolutionary material with electronic and structural properties that surpass conventional semiconductors and metals. Due to its superlative qualities, graphene is being considered as the reference material for a post-CMOS technology. Furthermore, graphene is also quite unusual electronically since its electric carriers behave as if they were massless and relativistic, the so-called Dirac particles. Because of its exotic electronic properties, theorists are being forced to revisit the conceptual basis for the theory of metals. Hence, graphene seems to be unveiling a new era in science and technology with still unseen consequences.

Decoherence is widely advocated as a panacea to explain how complex quantum systems behave classically. Viewed as a physical process, decoherence is widely recognised to be the single biggest obstacle to quantum computing. It is also discussed in contexts as varied as the early universe, mesoscopics and nanoscience, biophysical systems, and large-scale quantum phenomena in condensed matter and optical systems. But how does decoherence actually work? What are the mechanisms causing it, and how do these affect the real physical behaviour of such a wide variety of physical systems?

Only very recently has any kind of quantitative agreement been reached between predictive theory and real experiments, in investigations of decoherence on systems more complex than single atoms or molecules. This has been in work in superconducting cavities, and on large multi-spin magnetic molecules. These experiments test at least 3 different decoherence mechanisms simultaneously. Future development of the theory along with new experiments will not only be able to further test the ‘spin bath’ and ‘oscillator bath’ theories of environmental decoherence, but also check out more exotic ideas about ‘3rd-party decoherence’ and ‘intrinsic decoherence’ in Nature. It will also allow a much more rigorous look at one of the exciting new frontiers in this field, viz., the role decoherence plays in some biological processes.

This talk will introduce a general audience to this topic, and describe some of the recent progress (theoretical and experimental), as well as the outstanding questions.

When the electron beam possesses sufficient energy to displace carbon atoms from lattices, vacancies and insterstitials are created. Therefore, under specific beam conditions, one is able to create reactive sites (vacancies or divacancies) and reactive atoms (ad-toms or interstitials), that could start interacting between themselves or with other nanoparticles.

In this talk, we present from the theoretical and experimental standpoint, the effects of high electron irradiation at elevated temperatures on single-walled carbon nanotubes (SWNTs). Under these conditions, we witnessed the “welding” of SWNTs exhibiting various geometries. The nanotube welding mechanism is based on the formation and reconstructions of vacancies and divacancies, under the high electron beam, that result in the formation of molecular junctions involving 7 or 8 membered carbon rings. We will also show that controlled electron irradiation of MWNTs filled with metal nanowires, could cause large pressure buildup within the nanotube cores, to the extent of being able to plastically deform, extrude, and break the solid materials that are encapsulated inside. The pressure buildup is based on the creation and reconstruction of vacancies and divacancies that result in shrinkage of the tube diameter, which induces a compression of the encapsulated metals. However, when these vacancies are created, the displaced carbon atoms (interstitials) become very reactive and they could also be embedded in the encapsulated metal particle cores, which subsequently emerge as single- or multi-walled nanotubes inside the host nanotubes. These observations at atomic resolution in an electron microscope indicate that bulk diffusion of carbon through the body of catalytic particles is the nanotube growth-limiting process. When we combine electron irradiation effects and Joule heating we have been able to produce stable metal-nanotube heterostructures exhibiting covalently bonded interfaces between metal and carbon atoms. We will discuss that the electronic transport along these heterostructures is enhanced and it is due to the presence of covalent bonds established between the metal and the carbon atoms. Finally, novel results regarding the edge carbon atom reconstruction of graphene nanoribbons under electron beam irradiation and Joule heating, will be visited.

The phenomenon of exchange bias has remained something of a mystery since it was first discovered in core shell particles in 1956 [1]. Over the subsequent years many different models have been attempted to try and explain this effect most of which agree with some experimental data that can be found in the literature. However no single theory has ever been able to put a theoretical line consistently through data for different systems.
In this lecture the reason for our inability to explain exchange bias will be reviewed. Subsequently a new paradigm to explain exchange bias in sputtered polycrystalline films will be presented. This new paradigm is based on an original granular model due to Falcomer and Charap [2]. The basis of the new paradigm is that very careful thermal and magnetic cycling is required to ensure that the order in the antiferromagnetic grains is controlled carefully. Without such careful control reproducible data cannot be obtained.
These measurement procedures which are time consuming and complex, we refer to as the York Protocol and have been developed over the last 9 years. It will be shown that using the York Protocol and an extension of the former granular model, effects such as the film thickness dependence and grain size dependence of exchange bias can be fully explained with an excellent fit between theory and experiment [3]. The York Protocol also allows for the measurement of the anisotropy constant of antiferromagnetic grains [4].
The above model allows for an understanding of the behaviour of the individual AF grains in detail. Since the behaviour of the "bulk" of the antiferromagnetic grains is now known preliminary data describing the behaviour of the interface spins can now be distinguished from the behaviour of the bulk. Possible mechanisms for the behaviour of the interfaces themselves will also be presented.

[1] W. H. Meiklejohn, and C. P. Bean, Phys. Rev. 102 (1956) 1413.
[2] E. Fulcomer, and S. H. Charap, J. Appl. Phys. 43 (1972) 4190.
[3] G. Vallejo-Fernandez, L. E. Fernandez-Outon, and K. O'Grady, J. Phys. D: Appl. Phys.41 (2008) 112001.
[4] G. Vallejo-Fernandez, L. E. Fernandez-Outon, and K. O'Grady, Appl. Phys. Lett. 91 (2007) 212503.

Over the past decade, the sophistication of self and directed-assembly approaches for functional composite structures has increased dramatically, however, application of such structures in real-world systems has remained largely elusive, in part because such structures almost always contain finite defect densities. The storing, generating and harvesting of photons and electrons presents a unique opportunity for self-assembled composite materials. These applications are not only generally much more defect tolerant than for example self-assembled computational electronics, but also for these areas to make a substantive impact on the world energy situation, they must be produced in exceptionally large volume. In my talk, I will attempt to capture the state-of-the-art in highly functional self-assembled three-dimensional composites for energy harvesting and storage illustrated with examples from both my research and other groups with a particular focus on high charge and discharge rate nanostructured electrochemical energy storage systems (batteries and supercapacitors), and photonic crystals which exhibit unprecedented control over the absorption and emission of light (lasers, LEDs, and solar cells).

Aunque los naturalistas españoles del siglo XIX conocieron pronto, en 1860, la publicación de /On the Origin of Species/ (1859) de Charles Darwin, la primera traducción íntegra de esta obra al idioma español se retrasó hasta 1877. Un factor decisivo en la recepción del evolucionismo en España fue la influencia de las tradiciones científicas y culturales procedentes de Francia y Alemania. Durante el siglo XX continuó el debate sobre Darwin y la evolución tanto en la comunidad científica española como en la sociedad. La síntesis moderna de la evolución comenzó a ser común en los trabajos de los biólogos españoles a partir de la década de los años sesenta.

In my talk I will review different experimental results suggesting the existence of magnetic nanoscale free rotors. The nanoparticles are made of Fe2O3 which are dispersed in methanol based ferrofluid and CoFe2O4 inside a porous polymeric matrix. The data presented are magnetic and microwaves absorption. The mechanical rotation of these nano scale magnetic compasses is quantized being, therefore, the largest objects showing such quantum behaviour. It is important to remark that the data of our resonant absorption experiments have been interpreted by considering the rotational Doppler used to shift the frequency of the resonant absorption.

J. Tejada et al. J. Appl. Phys. 87, 8008 (2000).
J. Tejada et al. Phys. Rev. Lett. (January 2010) 

Although ice melts and water freezes under equilibrium conditions at 0ºC, water can be super-cooled under homogeneous conditions in a clean environment down to -40ºC without freezing. The influence of the electric field on the freezing temperature of super-cooled water (electro-freezing) is of topical importance in the living and inanimate worlds. We report that positively charged surfaces of the pyro-electric LiTaO3 crystals and the SrTiO3 thin films promote ice nucleation, whereas the same surfaces when negatively charged reduce the freezing temperature. Accordingly, droplets of water cooled down on a negatively charged Li TaO3 surface and remaining liquid at -11ºC freeze immediately by heating this surface to -8ºC, as a result of the replacement of the negative surface charge by a positive one. Furthermore, powder X-ray diffraction studies demonstrated that the freezing on the positively charged surface starts at the solid-water interface, whereas on a negatively charged surface ice nucleation starts at the air-water interface.

Contact: Yves Huttel, Agustina Asenjo