Opposition in Serbia: oppression, delegitimization and extra-institutional engagement

this chapter analyses the opposition’s position and role in Serbia in its evolution since the introduction of pluralism and the collapse of the communist regime. We observe the opposition during the last 30 years from the two main aspects: institutional and ideational. We also provide an overview of the contextual factors to show some specificities of the post-socialist democratisation process and democratic backsliding in Serbia. The institutional elements we observed provide insight into the actors’ formal position and power; they show us the main mechanisms and resources at the opposition’s disposal and evaluate the possible inequalities or disbalances of powers between the actors. Conversely, the ideational aspect shows the dominant narratives and relationships between the opposition and position. These narratives reflect the understanding of democracy and the role the opposition should play in the political system. They also reflect changes over time and enable us to understand different concepts of democracy and democratisation. The chapter is divided into four sections, corresponding to four different phases reflecting specific circumstances and dynamics. The first phase is the Milošević decade (1990-2000), which covers the initial transitional period, characterised by severe authoritarian tendencies and societal conflicts during the Yugoslav break-up process. The second phase, that of democratisation (2000-2012), starts from the Milošević defeat and initial institutional development, throughout the first troubles in the democratic transition and riffs in the ruling coalition. The third phase (2012-2020) begins with the second turnover of power and optimism about social consensus and the consolidation of democracy. However, it develops into competitive authoritarianism and almost complete annulation of pluralism. The final phase is short (so far) and ongoing – defined by the protest waves, boycotts of elections and Parliament, and the return of the opposition in the institutions

Effect of humidity on the writing speed and domain wall dynamics of ferroelectric domains

Altres ajuts: the ICN2 was funded by the CERCA programme / Generalitat de Catalunya.The switching dynamics of ferroelectric polarization under electric fields depends on the availability of screening charges in order to stabilize the switched polarization. In ferroelectrics, thin films with exposed surfaces investigated by piezoresponse force microscopy (PFM), the main source of external screening charges is the atmosphere and the water neck, and therefore relative humidity (RH) plays a major role. Here, it is shown how the dynamic writing of domains in BaTiO thin films changes by varying scanning speeds in the range of RH between 2.5% and 60%. The measurements reveal that the critical speed for domain writing, which is defined as the highest speed at which electrical writing of a continuous stripe domain is possible, increases non-monotonically with RH. Additionally, the width of line domains shows a power law dependence on the writing speed, with a growth rate coefficient decreasing with RH. The size of the written domains at a constant speed as well as the creep-factor μ describing the domain wall kinetics follow the behavior of water adsorption represented by the adsorption isotherm, indicating that the screening mechanism dominating the switching dynamics is the thickness and the structure of adsorbed water structure and its associated dielectric constant and ionic mobility

Tunable Molecular Electrodes for Bistable Polarization Screening

The polar discontinuity at any ferroelectric surface creates a depolarizing field that must be screened for the polarization to be stable. In capacitors, screening is done by the electrodes, while in bare ferroelectric surfaces it is typically accomplished by atmospheric adsorbates. Although chemisorbed species can have even better screening efficiency than conventional electrodes, they are subject to unpredictable environmental fluctuations and, moreover, dominant charged species favor one polarity over the opposite. This paper proposes a new screening concept, namely surface functionalization with resonance-hybrid molecules, which combines the predictability and bipolarity of conventional electrodes with the screening efficiency of adsorbates. Thin films of barium titanate (BaTiO) coated with resonant para-aminobenzoic acid (pABA) display increased coercivity for both signs of ferroelectric polarization irrespective of the molecular layer thickness, thanks to the ability of these molecules to swap between different electronic configurations and adapt their surface charge density to the screening needs of the ferroelectric underneath. Because electron delocalization is only in the vertical direction, unlike conventional metals, chemical electrodes allow writing localized domains of different polarity underneath the same electrode. In addition, hybrid capacitors composed of graphene/pABA/ferroelectric have been made with enhanced coercivity compared to pure graphene-electode capacitors

Oxidation processes at the surface of BaTiO3 thin films under environmental conditions

Altres ajuts: the ICN2 is funded by the CERCA programme/Generalitat de Catalunya. I. S. acknowledges support of the Secretaria d'Universitats i Recerca - Departament d'Empresa i Coneixement - Generalitat de Catalunya and the European Social Fund (ESF) (FI grant reference 2020 FI_B2 00157).Dissociation and adsorption of water on ferroelectric oxide surfaces play important role in the processes of screening and switching dynamics of ferroelectric polarization, as well as in catalytic processes which can be additionally coupled with light, temperature or vibration stimuli. In this work, we present XPS study of ferroelectric BaTiOthin films and determine the entanglement between surface chemistry, polarization direction and stability, by observing changes upon time exposure to environmental conditions, heating in Oatmosphere and irradiation in vacuum. We devote special attention to Ba 3d spectral region and identify two different oxidation states of O atoms in the compounds of Ba. While this second specie was generally attributed to Ba in surface compounds where it has different oxygen coordination than in the bulk, based on the XPS results of oxygen annealed thin films, we demonstrate that this so far neglected component, corresponds to barium peroxide (BaO) and identify it as important active specie for the study of screening mechanisms closely related with catalytic activity present in this ferroelectric material. Finally, we report on chemically assisted polarization switching in thin films induced by heating in vacuum or exposure to X-Ray radiation due to the formation of positive surface electric field created by oxygen or electron vacancies, respectively

Silver-induced γ→ε martensitic transformation in FeMn alloys : an experimental and computational study

Altres ajuts: acords transformatius de la UABPorous FeMn alloys with additions of 0, 1, 3 and 5 wt.% of Ag were fabricated using powder metallurgy and sintering. The microstructure of the fabricated alloys was characterized using X-ray diffraction, transmission electron microscopy and selected area electron diffraction. While equiatomic FeMn and FeMn-1Ag alloys possess a fully austenitic structure, a change in the crystallographic structure is observed upon addition of 3 and 5 wt.% of Ag, where a mixture of γ austenite and ε martensite phases is observed. Compression tests reveal that such structural transition causes an increase of the yield stress. The evolution of microstructure with the Ag content can be understood from theoretical calculations which show that Ag atoms prefer the intrinsic stacking fault (ISF) sites, revealing lower energy for the ε-like atomic plane sequence. This causes local depletion of the electronic charge, therefore weakening the interatomic bonds at the ISF plane and facilitating the phase transition. In addition, the total energy difference between the γ and ε phases decreases upon Ag addition. This enables the coexistence of both phases in the sample with 5 wt.% Ag. Both experimental and theoretical data agree that the magnetization value gradually increases upon Ag addition. This is due to the local stress that is introduced by Ag atoms, which expand the Ag-Fe and Ag-Mn first neighbour interatomic bonds compared to FeMn. This stress results in electronic charge that locally alters the Fe and Mn atomic magnetic moments. These results are appealing for the design of FeMn-based alloys with tuneable phase composition and physical properties for several technological application

Probing the Surface Polarization of Ferroelectric Thin Films by X-ray Standing Waves

Understanding the mechanisms underlying a stable polarization at the surface of ferroelectric thin films is of particular importance both from a fundamental point of view and to achieve control of the surface polarization itself. In this study, it is demonstrated that the X-ray standing wave technique allows the polarization near the surface of a ferroelectric thin film to be probed directly. The X-ray standing wave technique is employed to determine, with picometer accuracy, Ti and Ba atomic positions near the surface of three differently strained $\mathrm{BaTiO_3}$ thin films grown on scandate substrates, with a $\mathrm{SrRuO_3}$ film as bottom electrode. This technique gives direct access to atomic positions, and thus to the local ferroelectric polarization, within the first 3 unit cells below the surface. By employing X-ray photoelectron spectroscopy, a detailed overview of the oxygen-containing species adsorbed on the surface, upon exposure to ambient conditions, is obtained. The combination of structural and spectroscopic information allows us to conclude on the most plausible mechanisms that stabilize the surface polarization in the three samples under study. The different amplitude and orientation of the local ferroelectric polarizations are associated with surface charges attributed to the type, amount and spatial distribution of the oxygen-containing adsorbates

Effect of Humidity on the Writing Speed and Domain Wall Dynamics of Ferroelectric Domains

The switching dynamics of ferroelectric polarization under electric fields depends on the availability of screening charges in order to stabilize the switched polarization. In ferroelectrics, thin films with exposed surfaces investigated by piezoresponse force microscopy (PFM), the main source of external screening charges is the atmosphere and the water neck, and therefore relative humidity (RH) plays a major role. Here, it is shown how the dynamic writing of domains in BaTiO3 thin films changes by varying scanning speeds in the range of RH between 2.5% and 60%. The measurements reveal that the critical speed for domain writing, which is defined as the highest speed at which electrical writing of a continuous stripe domain is possible, increases non-monotonically with RH. Additionally, the width of line domains shows a power law dependence on the writing speed, with a growth rate coefficient decreasing with RH. The size of the written domains at a constant speed as well as the creep-factor μ describing the domain wall kinetics follow the behavior of water adsorption represented by the adsorption isotherm, indicating that the screening mechanism dominating the switching dynamics is the thickness and the structure of adsorbed water structure and its associated dielectric constant and ionic mobility.The authors want to acknowledge technical support from I. Gaponenko on the installation of the low-noise humidity controller. Financial support was obtained under projects from the Spanish Ministerio de Ciencia e Innovacion (MICINN) under projects PID2019-108573GB-C21, PID2019-109931GB-I00, and PID2019-110907GB-I00. In addition, this work was partially funded by 2017-SGR-579 from the Generalitat de Catalunya. The ICN2 was funded by the CERCA programme / Generalitat de Catalunya. The ICN2 was supported by the Severo Ochoa Centres of Excellence Programme, funded by the Spanish Research Agency (AEI, Grant no. SEV-2017-0706). The ICMAB was supported by the “Severo Ochoa” Program for Centers of Excellence in R&D (CEX2019-000917-S). I.S. acknowledges support of the Secretaria d'Universitats i Recerca - Departament d'Empresa i Coneixement - Generalitat de Catalunya and the European Social Fund (ESF) (FI grant reference 2020 FI_B2 00157).Peer reviewe

NiO core–shell nanostructure with ferromagnetic-like behavior at room temperature

International audienceWe report on ferromagnetic-like magnetic properties, at room temperature, of spherical nickel oxide core–shell nanoparticles synthesized by sol–gel combustion method. The sample is characterized by using transmission electron microscopy (TEM), selected electron area diffraction (SAED), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy (RS) and superconducting quantum interference device (SQUID) magnetometer. The SAED, EDX and RS show high quality and purity of the sample. The TEM images point to core–shell NiO nanostructure with a well crystallized NiO core and surface disorder shell. The size of the nanoparticles of about 5 nm and thickness of the surface shell below 1 nm are estimated from the TEM and HRTEM measurements. The measurements of the magnetization reveals ferromagnetic-like behavior of the sample at room temperature with remanent magnetization Mr = 0.0087 emu/g and coercive field HC = 115 Oe. These magnetic properties are quite different than in NiO bulk materials and uncommon for nanosized NiO materials. These results also indicate that the synthesized NiO core–shell nanostructure is suitable for spin-valve applications