References of "Journal of Physics : Condensed Matter"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailTowards understanding of magnetization reversal in Nd-Fe-B nanocomposites: analysis by high-throughput micromagnetic simulations
Erokhin, S.; Berkov, D.; Ito, M. et al

in Journal of Physics : Condensed Matter (2018), 30

We demonstrate how micromagnetic simulations can be employed in order to characterize and analyze the magnetic microstructure of nanocomposites. For the example of nanocrystalline Nd-Fe-B, which is a ... [more ▼]

We demonstrate how micromagnetic simulations can be employed in order to characterize and analyze the magnetic microstructure of nanocomposites. For the example of nanocrystalline Nd-Fe-B, which is a potential material for future permanent-magnet applications, we have compared three different models for the micromagnetic analysis of this material class: (i) a description of the nanocomposite microstructure in terms of Stoner-Wohlfarth particles with and without the magnetodipolar interaction; (ii) a model based on the core-shell representation of the nanograins; (iii) the latter model including a contribution of superparamagnetic clusters. The relevant parameter spaces have been systematically scanned with the aim to establish which micromagnetic approach can most adequately describe experimental data for this material. According to our results, only the last, most sophisticated model is able to provide an excellent agreement with the measured hysteresis loop. The presented methodology is generally applicable to multiphase magnetic nanocomposites and it highligths the complex interrelationship between the microstructure, magnetic interactions, and the macroscopic magnetic properties. [less ▲]

Detailed reference viewed: 60 (5 UL)
Full Text
Peer Reviewed
See detailLiquid crystals in micron-scale droplets, shells and fibers
Urbanski, Martin UL; Reyes, Catherine UL; Noh, Junghyun UL et al

in Journal of Physics : Condensed Matter (2017), 29

The extraordinary responsiveness and large diversity of self-assembled structures of liquid crystals are well documented and they have been extensively used in devices like displays. For long, this ... [more ▼]

The extraordinary responsiveness and large diversity of self-assembled structures of liquid crystals are well documented and they have been extensively used in devices like displays. For long, this application route strongly influenced academic research, which frequently focused on the performance of liquid crystals in display-like geometries, typically between flat, rigid substrates of glass or similar solids. Today a new trend is clearly visible, where liquid crystals confined within curved, often soft and flexible, interfaces are in focus. Innovation in microfluidic technology has opened for high-throughput production of liquid crystal droplets or shells with exquisite monodispersity, and modern characterization methods allow detailed analysis of complex director arrangements. The introduction of electrospinning in liquid crystal research has enabled encapsulation in optically transparent polymeric cylinders with very small radius, allowing studies of confinement effects that were not easily accessible before. It also opened the prospect of functionalizing textile fibers with liquid crystals in the core, triggering activities that target wearable devices with true textile form factor for seamless integration in clothing. Together, these developments have brought issues center stage that might previously have been considered esoteric, like the interaction of topological defects on spherical surfaces, saddle-splay curvature-induced spontaneous chiral symmetry breaking, or the non-trivial shape changes of curved liquid crystal elastomers with non-uniform director fields that undergo a phase transition to an isotropic state. The new research thrusts are motivated equally by the intriguing soft matter physics showcased by liquid crystals in these unconventional geometries, and by the many novel application opportunities that arise when we can reproducibly manufacture these systems on a commercial scale. This review attempts to summarize the current understanding of liquid crystals in spherical and cylindrical geometry, the state of the art of producing such samples, as well as the perspectives for innovative applications that have been put forward. [less ▲]

Detailed reference viewed: 189 (2 UL)
Full Text
Peer Reviewed
See detailTuning the work function of stepped metal surfaces by adsorption of organic molecules
Jiang, Yingda; Li, Jingtai; Su, Guirong et al

in Journal of Physics : Condensed Matter (2017), 29

Understanding the binding mechanisms for aromatic molecules on transition-metal surfaces, especially with defects such as vacancies, steps and kinks, is a major challenge in designing functional ... [more ▼]

Understanding the binding mechanisms for aromatic molecules on transition-metal surfaces, especially with defects such as vacancies, steps and kinks, is a major challenge in designing functional interfaces for organic devices. One important parameter in the performance of organic/inorganic devices is the barrier of charge carrier injection. In the case of a metallic electrode, tuning the electronic interface potential or the work function for electronic level alignment is crucial. Here, we use density-functional theory (DFT) calculations with van der Waals (vdW) interactions treated with both screened pairwise (vdWsurf) and many-body dispersion (MBD) methods, to systematically study the interactions of benzene with a variety of stepped surfaces. Our calculations confirm the physisorptive character of Ag(2 1 1), Ag(5 3 3), Ag(3 2 2), Ag(7 5 5) and Ag(5 4 4) surfaces upon the adsorption of benzene. The MBD effects reduce the adsorption energies by about 0.15 eV per molecule compared to the results from the DFT + vdWsurf method. In addition, we find that the higher the step density, the larger the reduction of the work function upon the adsorption of benzene. We also study the effect of vdW interactions on the electronic structure using a fully selfconsistent implementation of the vdWsurf method in the Kohn–Sham DFT framework. We find that the self-consistent vdWsurf effects increase the work function due to the lowered Fermi level and the increased vacuum level. As a result, the benzene/Ag(2 1 1) system has the lowest work function (3.67 eV) among the five adsorption systems, significantly smaller than the work function of the clean Ag(1 1 1) surface (4.74 eV). Our results provide important insights into the stability and electronic properties of molecules adsorbed on stepped metal surfaces, which could help in designing more appropriate interfaces with low work functions for electron transfer. [less ▲]

Detailed reference viewed: 97 (2 UL)
Full Text
Peer Reviewed
See detailSmall-angle neutron scattering of nanocrystalline gadolinium and holmium with random paramagnetic susceptibility
Döbrich, Frank; Bick, Jens-Peter; Birringer, Rainer et al

in Journal of Physics : Condensed Matter (2015), 27

Detailed reference viewed: 75 (4 UL)
Full Text
Peer Reviewed
See detailMagnetic small-angle neutron scattering of bulk ferromagnets
Michels, Andreas UL

in Journal of Physics : Condensed Matter (2014), 26

Detailed reference viewed: 68 (3 UL)
Full Text
Peer Reviewed
See detailCritical behaviour of nanocrystalline gadolinium: evidence for random uniaxial dipolar universality class
Ferdinand, A.; Probst, A.-C.; Michels, Andreas UL et al

in Journal of Physics : Condensed Matter (2014), 26

Detailed reference viewed: 61 (7 UL)
Full Text
Peer Reviewed
See detailAnisotropic optical response of GaN and AlN nanowires
Molina-Sanchez, Alejandro UL; García-Cristóbal, A.

in Journal of Physics : Condensed Matter (2012), 24(29), 295301

We present a theoretical study of the electronic structure and optical properties of free-standing GaN and AlN nanowires. We have implemented the empirical tight-binding method, with an orbital basis sp 3 ... [more ▼]

We present a theoretical study of the electronic structure and optical properties of free-standing GaN and AlN nanowires. We have implemented the empirical tight-binding method, with an orbital basis sp 3 , that includes the spin–orbit interaction. The passivation of the dangling bonds at the free surfaces is also studied, together with the effects on the electronic structure of the nanowire. For both GaN and AlN nanowires, we have found a remarkable anisotropy of the optical absorption when the light-polarization changes, showing in the case of GaN a dependence on the nanowire size. [less ▲]

Detailed reference viewed: 66 (2 UL)
Full Text
Peer Reviewed
See detailRotational diffusion of magnetic nickel nanorods in colloidal dispersions
Günther, Annegret UL; Bender, Philipp; Tschöpe, Andreas et al

in Journal of Physics : Condensed Matter (2011), 23

Colloidal dispersions of Ni nanorods were synthesized by pulsed electrodeposition of Ni into nanoporous aluminum oxide layers followed by dissolution of the templates. Geometrical characterization of the ... [more ▼]

Colloidal dispersions of Ni nanorods were synthesized by pulsed electrodeposition of Ni into nanoporous aluminum oxide layers followed by dissolution of the templates. Geometrical characterization of the nanorods by transmission electron microscopy and scanning electron microscopy allowed us to determine the average length (100–250 nm) and diameter (20–40 nm) of the rods and to estimate the thickness of the polyvinylpyrrolidone surfactant layer. Due to their acicular shape, nanorods of the given size are uniaxial ferromagnetic single domain particles and exhibit a distinct anisotropic polarizability. These two characteristic properties are the physical basis for magnetic field-dependent optical transmission and allow us to investigate the rotational diffusion of the nanorods in liquid dispersion. In the present study, we employed AC magnetization measurements, dynamical light scattering and optical transmission measurements in a rotating magnetic field to determine the rotational diffusion coefficient. The results from all three methods were consistent and agree with theory within a factor of 2. [less ▲]

Detailed reference viewed: 33 (4 UL)
Full Text
Peer Reviewed
See detailNeutron spin-flip scattering of nanocrystalline cobalt
Honecker, Dirk UL; Döbrich, Frank UL; Dewhurst, C. D. et al

in Journal of Physics : Condensed Matter (2011), 23(1), 1-4

Detailed reference viewed: 35 (1 UL)
Full Text
Peer Reviewed
See detailGrain-boundary-induced spin disorder in nanocrystalline gadolinium
Döbrich, Frank UL; Elmas, M.; Ferdinand, A. et al

in Journal of Physics : Condensed Matter (2009), 21(15), 1560031-1560035

Based on experimental magnetic-field-dependent neutron scattering data, we have calculated the autocorrelation function of the spin misalignment of nanocrystalline 160gadolinium. The analysis suggests the ... [more ▼]

Based on experimental magnetic-field-dependent neutron scattering data, we have calculated the autocorrelation function of the spin misalignment of nanocrystalline 160gadolinium. The analysis suggests the existence of two characteristic length scales in the spin system: the smaller one is about 5 nm and is attributed to the defect cores of the grain boundaries, whereas the larger length scale is of the order of the average crystallite size D = 21 nm and presumably describes the response of the magnetization to the magnetic anisotropy field of the individual crystallites. [less ▲]

Detailed reference viewed: 39 (1 UL)
Full Text
Peer Reviewed
See detailSecond order elasticity at hypersonic frequencies of reactive polyurethanes as seen by generalized Cauchy relations.
Philipp, Martine UL; Vergnat, Christelle; Müller, Ulrich UL et al

in Journal of Physics : Condensed Matter (2009), 21

The non-equilibrium process of polymerization of reactive polymers can be accompanied by transition phenomena like gelation or the chemical glass transition. The sensitivity of the mechanical properties ... [more ▼]

The non-equilibrium process of polymerization of reactive polymers can be accompanied by transition phenomena like gelation or the chemical glass transition. The sensitivity of the mechanical properties at hypersonic frequencies—including the generalized Cauchy relation—to these transition phenomena is studied for three different polyurethanes using Brillouin spectroscopy. As for epoxies, the generalized Cauchy relation surprisingly holds true for the non-equilibrium polymerization process and for the temperature dependence of polyurethanes. Neither the sol–gel transition nor the chemical and thermal glass transitions are visible in the representation of the generalized Cauchy relation. Taking into account the new results and combining them with general considerations about the elastic properties of the isotropic state, an improved physical foundation of the generalized Cauchy relation is proposed. [less ▲]

Detailed reference viewed: 41 (1 UL)
Full Text
Peer Reviewed
See detailInfluence of Al2O3 nanoparticles on the isothermal cure of an epoxy resin
Sanctuary, Roland UL; Krüger, Jan-Kristian UL; Baller, Jörg UL et al

in Journal of Physics : Condensed Matter (2009), 21

The influence of Al2O3 nanoparticles on the curing of an epoxy thermoset based on diglycidyl ether of bisphenol A was investigated using temperature-modulated differential scanning calorimetry (TMDSC) and ... [more ▼]

The influence of Al2O3 nanoparticles on the curing of an epoxy thermoset based on diglycidyl ether of bisphenol A was investigated using temperature-modulated differential scanning calorimetry (TMDSC) and rheology. Diethylene triamine was used as a hardener. TMDSC not only allows for a systematic study of the kinetics of cure but simultaneously gives access to the evolution of the specific heat capacities of the thermosets. The technique thus provides insight into the glass transition behaviour of the nanocomposites and hence makes it possible to shed some light on the interaction between the nanoparticles and the polymer matrix. The Al2O3 fillers are shown to accelerate the growth of macromolecules upon isothermal curing. Several mechanisms which possibly could be responsible for the acceleration are described. As a result of the faster network growth chemical vitrification occurs at earlier times in the filled thermosets and the specific reaction heat decreases with increasing nanoparticle concentration. Rheologic measurements of the zero-shear viscosity confirm the faster growth of the macromolecules in the presence of the nanoparticles. [less ▲]

Detailed reference viewed: 58 (1 UL)
Full Text
Peer Reviewed
See detailChemically induced transition phenomena in polyurethanes as seen from generalized mode Grüneisen parameters.
Müller, Ulrich UL; Philipp, Martine UL; Bactavatchalou, R. et al

in Journal of Physics : Condensed Matter (2008), 20(20), 205101-205108

Many phenomenological properties of reactive polymers like polyurethanes increase or decrease continuously in the course of the curing process before saturating at the end of the chemical reaction. This ... [more ▼]

Many phenomenological properties of reactive polymers like polyurethanes increase or decrease continuously in the course of the curing process before saturating at the end of the chemical reaction. This holds true for instance for the mass density, the refractive index, the chemical turnover and the hypersonic properties. The reason for this monotone behaviour is that the chemical reaction behaves like a continuous succession of irreversible phase transitions. These transitions are superposed by the sol–gel transition and possibly by the chemically induced glass transition, with the drawback that the latter two highlighted transitions are often hidden by the underlying curing process. In this work we propose generalized mode Grüneisen parameters as an alternative probe for elucidating the polymerization process itself and the closely related transition phenomena. As a model system we use polyurethane composed of a diisocyanate and varying ratios of difunctional and trifunctional alcohols. [less ▲]

Detailed reference viewed: 30 (1 UL)
Full Text
Peer Reviewed
See detailSuspensions of rod-like colloids and a depleting agent under confinement
Jungblut, S.; Binder, K.; Schilling, Tanja UL

in Journal of Physics : Condensed Matter (2008), 20(40),

Detailed reference viewed: 48 (3 UL)
Peer Reviewed
See detailThe role of the CdS buffer layer in CuGaSe2-based solar cells
Caballero, Raquel; Kaufmann, Christian A.; Cwil, Michael et al

in Journal of Physics : Condensed Matter (2007), 19(35), 356222-32

Detailed reference viewed: 71 (0 UL)
Full Text
Peer Reviewed
See detailSelf-poisoning of crystal nuclei in hard-rod liquids
Schilling, Tanja UL; Frenkel, Daan

in Journal of Physics : Condensed Matter (2004), 16(19), 2029-2036

We report a Monte Carlo study of the pathway for crystal nucleation in a fluid of hard, colloidal rods. In the earliest stages of nucleation, a lamellar crystallite forms. Subsequent thickening of this ... [more ▼]

We report a Monte Carlo study of the pathway for crystal nucleation in a fluid of hard, colloidal rods. In the earliest stages of nucleation, a lamellar crystallite forms. Subsequent thickening of this lamella is hampered by the fact that the top and bottom surfaces of this crystallite are preferentially covered by rods that align parallel to the surface. As a consequence, subsequent growth of individual crystals is stunted. Experimental evidence for such stunted crystal growth has recently been reported by Maeda and Maeda in experiments on suspensions of colloidal rods [Phys. Rev. Lett. 90, 018303 (2003)]. The simulations suggest that, in experiments, the growth of multilayer colloidal crystals can be selectively enhanced by the application of an external aligning field. [less ▲]

Detailed reference viewed: 35 (2 UL)
Full Text
Peer Reviewed
See detailElastic properties of single-crystalline and consolidated nano-structured yttrium oxide at room temperature.
Baller, Jörg UL; Krüger, Jan-Kristian UL; Birringer, R. et al

in Journal of Physics : Condensed Matter (2000), 12(25), 5403-5409

High resolution Brillouin spectroscopy was used to characterize the elastic stiffness properties of consolidated nano-crystalline yttrium oxide as well as of the related single-crystalline state. Defect ... [more ▼]

High resolution Brillouin spectroscopy was used to characterize the elastic stiffness properties of consolidated nano-crystalline yttrium oxide as well as of the related single-crystalline state. Defect enriched grain boundaries are discussed as sources for the extremely soft elastic properties of the nano-crystalline state. [less ▲]

Detailed reference viewed: 23 (0 UL)