Exchange coupling between magnetic layers across non-magnetic superlattices

The oscillation periods of the interlayer exchange coupling are investigated when two magnetic layers are separated by a metallic superlattice of two distinct non-magnetic materials. In spite of the conventional behaviour of the coupling as a function of the spacer thickness, new periods arise when the coupling is looked upon as a function of the number of cells of the superlattice. The new periodicity results from the deformation of the corresponding Fermi surface, which is explicitly related to a few controllable parameters, allowing the oscillation periods to be tuned.Comment: 13 pages; 5 figures; To appear in J. Phys.: Cond. Matte

Aggregation in a mixture of Brownian and ballistic wandering particles

In this paper, we analyze the scaling properties of a model that has as limiting cases the diffusion-limited aggregation (DLA) and the ballistic aggregation (BA) models. This model allows us to control the radial and angular scaling of the patterns, as well as, their gap distributions. The particles added to the cluster can follow either ballistic trajectories, with probability $P_{ba}$, or random ones, with probability $P_{rw}=1-P_{ba}$. The patterns were characterized through several quantities, including those related to the radial and angular scaling. The fractal dimension as a function of $P_{ba}$ continuously increases from $d_f\approx 1.72$ (DLA dimensionality) for $P_{ba}=0$ to $d_f\approx 2$ (BA dimensionality) for $P_{ba}=1$. However, the lacunarity and the active zone width exhibt a distinct behavior: they are convex functions of $P_{ba}$ with a maximum at $P_{ba}\approx1/2$. Through the analysis of the angular correlation function, we found that the difference between the radial and angular exponents decreases continuously with increasing $P_{ba}$ and rapidly vanishes for $P_{ba}>1/2$, in agreement with recent results concerning the asymptotic scaling of DLA clusters.Comment: 7 pages, 6 figures. accepted for publication on PR

Modelling of epitaxial film growth with a Ehrlich-Schwoebel barrier dependent on the step height

The formation of mounded surfaces in epitaxial growth is attributed to the presence of barriers against interlayer diffusion in the terrace edges, known as Ehrlich-Schwoebel (ES) barriers. We investigate a model for epitaxial growth using a ES barrier explicitly dependent on the step height. Our model has an intrinsic topological step barrier even in the absence of an explicit ES barrier. We show that mounded morphologies can be obtained even for a small barrier while a self-affine growth, consistent with the Villain-Lai-Das Sarma equation, is observed in absence of an explicit step barrier. The mounded surfaces are described by a super-roughness dynamical scaling characterized by locally smooth (faceted) surfaces and a global roughness exponent $\alpha>1$. The thin film limit is featured by surfaces with self-assembled three-dimensional structures having an aspect ratio (height/width) that may increase or decrease with temperature depending on the strength of step barrier.Comment: To appear in J. Phys. Cond. Matter; 3 movies as supplementary materia

Exponential behavior of the interlayer exchange coupling across non-magnetic metallic superlattices

It is shown that the coupling between magnetic layers separated by non-magnetic metallic superlattices can decay exponentially as a function of the spacer thickness $N$, as opposed to the usual $N^{-2}$ decay. This effect is due to the lack of constructive contributions to the coupling from extended states across the spacer. The exponential behavior is obtained by properly choosing the distinct metals and the superlattice unit cell composition.Comment: To appear in Phys. Rev.

Engaging tourists with museums in the destination Lisbon

The aim of this study is to analyze the relationships among the concepts of serious leisure and museum prestige on engagement with museums, pleasant emotions, memory, and word-of-mouth among Lisbon tourists. Findings reveal that reflective motivations are one important driver of engagement. Be engaged with museums lead to create positive emotions and memories, which, in turn, contribute to the willingness to communicate and recommend the Lisbon museums to others.info:eu-repo/semantics/publishedVersio

Tourists’ lifestyle and foodservice tendencies in social media

This chapter reviews the literature on gastronomy tourism and provides an overview of the most important characteristic features of the fieldwork methodology. It examines the influence of lifestyle changes and the effect that Web 2.0 had on gastronomic tourism. Although literature proposes a link between tourism and gastronomy, there is a need to deepen the understanding of the perspective and opinion of tourists as end users of activities related to culinary tourism. Tourists want to have new food experiences, local food, and traditions, but, they need to know what is healthy or less healthy. The foodservice market has been suffering a strong impact from Asian food. All over the world, international tourism flows and receipts have been consolidating their growing tendencies, becoming a major category of international trade in services and therefore providing a high relevance in stimulating economic growth. Taking into account the market transformations, foodservice market has adopted a more social responsibility and accountability in their daily procedures.info:eu-repo/semantics/acceptedVersio

How customer experience attributes influence customer satisfaction and online bank credibility

WOS:000427297600065 (Nº de Acesso Web of Science)The banking sector has been focused its attention towards attracting Generation Upsilon since they have consolidated as a huge force with powerful spending power which will unavoidably rival with Baby Boomers' market dominance. Thus, this article analyses customer experience of Generation Upsilon and its effect on customer satisfaction and bank credibility. Empirical evidence, based on primary data from an online survey (550 questionnaires were spread over a two-month period in 2016 but only 205 were usable and completed) reveal that the customer experience attributes (mainly executional excellence and reputation) have a positive relationship on credibility and satisfaction. In addition, "Value for money", "Getting things right the first time" and "Put the consumer first" emerge as the most importance attributes for Generation Upsilon in experiencing the bank

Tourism in São Tomé and Principe: the forgotten pearl

São Tomé and Príncipe is a small African country, which has been facing several vulnerabilities and constraints that have been limiting its development process since its independence. Hence, it is vital to improve alternative ways of development, in order to overcome this disadvantage. This article analyses São Tomé and Príncipe tourism destination competitiveness based on 27 interviews conducted in São Tomé and Príncipe. The conclusions show that the main qualify determinants are: the natural resources, the unique landscape, the cocoa and coffee plantations, the friendly locals and the peace and safety. But, on the other hand, this country reveals a competitive weakness, mainly due to the lack of infrastructures, technical training for hospitality and tourism, coordination among ministries, inter-relationship among public, private and non-profit organizations, as well as external marketing communication

Integrable theories and loop spaces: fundamentals, applications and new developments

We review our proposal to generalize the standard two-dimensional flatness construction of Lax-Zakharov-Shabat to relativistic field theories in d+1 dimensions. The fundamentals from the theory of connections on loop spaces are presented and clarified. These ideas are exposed using mathematical tools familiar to physicists. We exhibit recent and new results that relate the locality of the loop space curvature to the diffeomorphism invariance of the loop space holonomy. These result are used to show that the holonomy is abelian if the holonomy is diffeomorphism invariant. These results justify in part and set the limitations of the local implementations of the approach which has been worked out in the last decade. We highlight very interesting applications like the construction and the solution of an integrable four dimensional field theory with Hopf solitons, and new integrability conditions which generalize BPS equations to systems such as Skyrme theories. Applications of these ideas leading to new constructions are implemented in theories that admit volume preserving diffeomorphisms of the target space as symmetries. Applications to physically relevant systems like Yang Mills theories are summarized. We also discuss other possibilities that have not yet been explored.Comment: 64 pages, 8 figure

Local roughness exponent in the nonlinear molecular-beam-epitaxy universality class in one-dimension

We report local roughness exponents, $\alpha_{\text{loc}}$, for three interface growth models in one dimension which are believed to belong the non-linear molecular-beam-epitaxy (nMBE) universality class represented by the Villain-Lais-Das Sarma (VLDS) stochastic equation. We applied an optimum detrended fluctuation analysis (ODFA) [Luis et al., Phys. Rev. E 95, 042801 (2017)] and compared the outcomes with standard detrending methods. We observe in all investigated models that ODFA outperforms the standard methods providing exponents in the narrow interval $\alpha_{\text{loc}}\in[0.96,0.98]$ consistent with renormalization group predictions for the VLDS equation. In particular, these exponent values are calculated for the Clarke-Vvdensky and Das Sarma-Tamborenea models characterized by very strong corrections to the scaling, for which large deviations of these values had been reported. Our results strongly support the absence of anomalous scaling in the nMBE universality class and the existence of corrections in the form $\alpha_{\text{loc}}=1-\epsilon$ of the one-loop renormalization group analysis of the VLDS equation