Quantum Phase Transition in Pr2CuO4 to Collinear Spin State in Inclined Magnetic Field: A Neutron Diffraction Observation

In the external field slightly inclined to the $x$- or y-axis of the frustrated tetragonal atiferromagnet Pr2CuO4, a transition is discovered from the phase with orthogonal antiferromagnetic spin subsystems along [1,0,0] and [0,1,0] to the phase with the collinear spins. This phase is shown to be due to the pseudodipolar interaction, and transforms into the spin-flop phase S perp H asymptotically at very high field. The discovered phase transition holds at T=0 and is a quantum one, with the transition field being the critical point and the angle between two subsystems being the order parameter

The de Haas-van Alphen effect across the metamagnetic transition in Sr3_3Ru2_2O7_7

We report a study of the de Haas-van Alphen (dHvA) effect on the itinerant metamagnet Sr$_3$Ru$_2$O$_7$. Extremely high sample purity allows the observation of dHvA oscillations both above and below the metamagnetic transition field of 7.9 T. The quasiparticle masses are fairly large away from the transition, and are enhanced by up to an extra factor of three as the transition is approached, but the Fermi surface topography change is quite small. The results are qualitatively consistent with a field-induced Stoner transition in which the mass enhancement is the result of critical fluctuations.Comment: 4 pages, 3 figure

The balancing act between high electronic and low ionic transport influenced by perovskite grain boundaries

\ua9 2024 The Royal Society of Chemistry.A better understanding of the materials\u27 fundamental physical processes is necessary to push hybrid perovskite photovoltaic devices towards their theoretical limits. The role of the perovskite grain boundaries is essential to optimise the system thoroughly. The influence of the perovskite grain size and crystal orientation on physical properties and their resulting photovoltaic performance is examined. We develop a novel, straightforward synthesis approach that yields crystals of a similar size but allows the tuning of their orientation to either the (200) or (002) facet alignment parallel to the substrate by manipulating dimethyl sulfoxide (DMSO) and tetrahydrothiophene-1-oxide (THTO) ratios. This decouples crystal orientation from grain size, allowing the study of charge carrier mobility, found to be improved with larger grain sizes, highlighting the importance of minimising crystal disorder to achieve efficient devices. However, devices incorporating crystals with the (200) facet exhibit an s-shape in the current density-voltage curve when standard scan rates are used, which typically signals an energetic interfacial barrier. Using the drift-diffusion simulations, we attribute this to slower-moving ions (mobility of 0.37 7 10-10 cm2 V-1 s-1) in combination with a lower density of mobile ions. This counterintuitive result highlights that reducing ion migration does not necessarily minimise hysteresis

Nanostructured diblock copolymer films with embedded magnetic nanoparticles

Nanostructured diblock copolymer films with embedded magnetic nanoparticles are prepared by solution casting. The diblock copolymer polystyrene-block-polymethylmethacrylate with a fully deuterated polystyrene block of a weight ratio of 0.22 is used as a structure-directing matrix. Maghemite nanoparticles (gamma-Fe2O3) are coated with polystyrene and thus have a selective affinity to the minority block of the diblock copolymer. The hybrid film morphology is investigated as a function of nanoparticle concentration. The surface structure is probed with atomic force microscopy and scanning electron microscopy. The inner film structure and the structure at the polymer-substrate interface are detected with grazing incidence small angle neutron scattering (GISANS). Irrespective of the nanoparticle concentration a well developed micro-phase separation structure is present. From the Bragg peaks observed in the GISANS data a linear nanoparticle concentration dependence of the inter-domain spacing of the micro-phase separation structure is determined. The superparamagnetic and blocking behavior can be explained with a generalized Stoner-Wohlfarth-Neel theory which includes either an elastic torque being exerted on the nanoparticles by the field or a broad distribution of anisotropy constants

Nucleated dewetting of thin polymer films

A combination of optical microscopy and neutron reflectometry is utilized to investigate the dewetting caused by a nucleation and growth process. The model system is polystyrene (PS) on top of Si (100) with its native oxide layer. Nucleation is forced by the introduction of additional grains during the sample preparation. From neutron scattering the density profile as an averaged piece of information is gained. Optical microscopy enables the in-situ determination of lateral local structures. The growth of the hole area of individual holes is described within the Kolmogorov model. The growth exponent as a function of annealing time of all holes investigated shows a linear increase

Molecular versus macroscopic perspective on the demixing transition of aqueous PNIPAM solutions by studying the dual character of the refractive index

The phase separation of aqueous poly(N-isopropyl acrylamide) (PNIPAM) solutions is known to strongly affect their volume expansion behaviour and the elastic moduli, as the latter are strongly coupled to the macroscopic order parameter. On the molecular scale, considerable changes in H-bonding and hydrophobic interactions, as well as in the structure govern the demixing process. However, the relationship between the molecular and macroscopic order parameters is unclear for such complex phase-separating solutions. We contribute to the clarification of this problem by relating optical to volumetric properties across the demixing transition of dilute to concentrated aqueous PNIPAM solutions. Far from the demixing temperature, the temperature dependence of the refractive index is predominantly determined by thermal expansion. In the course of phase separation, the refractive index is dominated by the anomalous behaviour of the specific refractivity, which reflects the spatio-temporally averaged changes in molecular interactions and the structural reorganization of the demixing solutions. Moreover, the presence of relaxation processes is studied by the complex expansion coefficient using the novel technique of temperature modulated optical refractometry

Crossmedia & Storytelling i Marknadsföringssyfte

This paper contains a study where we apply cross media and storytelling into the design process of a practical commercial campaign. The purpose is to learn more and deeper by using cross media and the ideal of storytelling practical. We applied a qualitative method for research of the project to provide a high-quality empirical work. The result shows that by using well-structured story early in the design process you will easily succeed with your cross media design