Magnetic, electronic, and structural properties of MFe 2 O 4 (M = Mg,Zn,Fe) ferric spinels have been studied by 57 Fe Mössbauer spectroscopy, electrical conductivity, and powder and single-crystal x-ray diffraction (XRD) to a pressure of 120 GPa and in the 2.4-300 K temperature range. These studies reveal for all materials, at the pressure range 25-40 GPa, an irreversible first-order structural transition to the postspinel CaTi 2 O 4 − type structure (Bbmm) in which the HS Fe 3+ occupies two different crystallographic sites characterized by six-and eightfold coordination polyhedra, respectively. Above 40 GPa, an onset of a sluggish second-order high-to-low spin (HS-LS) transition is observed on the octahedral Fe 3+ sites while Fe 3+ occupying bicapped trigonal prism sites remain in the HS state. Despite an appreciable resistance decrease, corroborating with the transition to the LS state, MgFe 2 O 4 and ZnFe 2 O 4 remain semiconductors at this pressure range. However, in the case of Fe 3 O 4 , the second-order HS-LS transition on the Fe 3+ octahedral sites corroborates with a clear trend to a gap closure and formation of a semimetal state above 50 GPa. Above 65 GPa, another structural phase transition is observed in Fe 3 O 4 to a new Pmma structure. This transition coincides with the onset of nonmagnetic Fe 2+ , signifying further propagation of the gradual collapse of magnetism corroborating with a sluggish metallization process. With this, half of Fe 3+ sites remain in the HS state. Thus, this paper demonstrates that, in a material with a complex crystal structure containing transition metal cation(s) in different environments, a HS-LS transition and delocalization/metallization of the 3d electrons does not necessarily occur simultaneously and may propagate through different crystallographic sites at different degrees of compression.

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Suspensions of charged nanoparticles near an isolated like-charged interface show a particle-free region, which is followed by a damped, oscillatory concentration profile.

Alpha-Synuclein (AS) is the protein playing the major role in Parkinson's disease (PD), a neurological disorder characterized by the degeneration of dopaminergic neurons and the accumulation of AS into amyloid plaques. The aggregation of AS into intermediate aggregates, called oligomers, and their pathological relation with biological membranes are considered key steps in the development and progression of the disease. Here we propose a multi-technique approach to study the effects of AS in its monomeric and oligomeric forms on artificial lipid membranes containing GM1 ganglioside. GM1 is a component of functional membrane micro-domains, called lipid rafts, and has been demonstrated to bind AS in neurons. With the aim to understand the relation between gangliosides and AS, here we exploit the complementarity of microscopy (Atomic Force Microscopy) and neutron scattering (Small Angle Neutron Scattering and Neutron Reflectometry) techniques to analyze the structural changes of two different membranes (Phosphatidylcholine and Phosphatidylcholine/GM1) upon binding with AS. We observe the monomer-and oligomer-interactions are both limited to the external membrane leaflet and that the presence of ganglioside leads to a stronger interaction of the membranes and AS in its monomeric and oligomeric forms with a stronger aggressiveness in the latter. These results support the hypothesis of the critical role of lipid rafts not only in the biofunctioning of the protein, but even in the development and the progression of the Parkinson's disease. and SANS-YS instruments of the Budapest Neutron Center. High purity functionalization of the Si block surface by the staff of the BioMEMS group of Inst. Tech. Physics and Mater.

The multilayer of approximate structure MgO(100)/[ n fe 51 Rh 49 (63 Å)/ 57 fe 51 Rh 49 (46 Å)] 10 deposited at 200 °C is primarily of paramagnetic A1 phase and is fully converted to the magnetic B2 phase by annealing at 300 °C for 60 min. Subsequent irradiation by 120 keV Ne + ions turns the thin film completely to the paramagnetic A1 phase. Repeated annealing at 300 °C for 60 min results in 100% magnetic B2 phase, i.e. a process that appears to be reversible at least twice. The A1 → B2 transformation takes place without any plane-perpendicular diffusion while Ne + irradiation results in significant interlayer mixing. Besides the traditional "faster-smaller-cheaper" directive, a new requirement has recently arisen for the newly developed devices: the energy efficiency. The electricity consumption of information technology is expected to reach 13% of the global utilization in the next decade 1,2 , of which nearly 50% is due to unwanted heat dissipation. Therefore, the study of novel materials and developing new operation principles for energy-saving applications in information technology are essential for supporting sustainable development. From this point of view, the fine control of magnetism is a great step towards reducing energy consumption of information storage by orders of magnitude 3-11. The Fe-Rh system is an excellent playground for developing energy-efficient magnetic devices 12,13. The equilibrium phase diagram of solid Fe-Rh 14,15 includes a great variety of phases of different magnetic behaviour. The disordered bcc A2 (α or δ, prototype W) phases are, depending on temperature, ferro-or paramagnetic (PM). The ordered bcc B2 (α' or α'' , prototype CsCl) phases show ferro-, antiferro-or paramagnetism at different temperatures and concentrations. The disordered fcc A1 (γ, prototype Cu) phase is PM at all investigated temperatures. The existence of a monoclinic antiferromagnetic (AFM) ground state was predicted by DFT calculations in the equiatomic FeRh alloy in 2016 16. However, this phase could not be identified in thin films by Wolloch and co-workers 17. Using nuclear resonant inelastic X-ray scattering (NRIXS), these latter authors analysed the lattice dynamical contribution to the phase stability in FeRh and demonstrated that the AFM ground state was stabilized by phonon softening. With increasing temperature, the nearly equiatomic FeRh alloy of B2 structure undergoes a metamagnetic transition from the low-temperature AFM α'' to the high-temperature ferromagnetic (FM) α' phase close to room temperature (RT) 18-27. In the AFM phase, Fe atoms carry a magnetic moment of 3.3 μ B of alternating direction while the Rh atoms possess inconsiderable magnetic moment 22. Conversely, in the FM phase, Fe and Rh atoms carry parallel moments of 3.2 μ B and 0.9 μ B , respectively 28-30. This magnetic transition is accompanied with a reduction of the resistivity and an ~ 0.6% isotropic strain of the crystal lattice 21,31. By introducing strain in the FeRh crystal lattice, this phenomenon can be reversed and the mag...

Reducing the material sizes to the nanometer length scale leads to drastic modifications of the propagating lattice excitations (phonons) and their interactions with electrons and magnons.

Extracellular vesicles (EVs) are a potent intercellular communication system. Such small vesicles transport biomolecules between cells and throughout the body, strongly influencing the fate of recipient cells. Due to their...

Self-organized silicide nanowires are considered as building blocks of future nanoelectronics and have been intensively investigated. In nanostructures, the lattice vibrational waves (phonons) deviate drastically from those in bulk crystals, which gives rise to anomalies in thermodynamic, elastic, electronic, and magnetic properties. Hence a thorough understanding of the physical properties of these materials requires a comprehensive investigation of the lattice dynamics as a function of the nanowire size. We performed a systematic lattice dynamics study of endotaxial FeSi 2 nanowires, forming the metastable, surface-stabilized α phase, which are in-plane embedded into the Si(110) surface. The average widths of the nanowires ranged from 24 to 3 nm, and their lengths ranged from several micrometers to about 100 nm. The Fe-partial phonon density of states, obtained by nuclear inelastic scattering, exhibits a broadening of the spectral features with decreasing nanowire width. The experimental data obtained along and across the nanowires unveiled a pronounced vibrational anisotropy that originates from the specific orientation of the tetragonal α-FeSi 2 unit cell on the Si(110) surface. The results from first-principles calculations are fully consistent with the experimental observations and allow for a comprehensive understanding of the lattice dynamics of endotaxial silicide nanowires.