1,794 research outputs found
Early stages of mechanical crystallization of amorphous FeZrBCu soft magnetic material
No full textEarly stages of mechanical crystallization of amorphous FeZrBCu soft magnetic material / J. Friedrich, U. Herr, K. Samwer. – In: Journal of applied physics. 87. 2000. S. 2464-246
Reply to Comment on ‘Disentangling interatomic repulsion and anharmonicity in the viscosity and fragility of glasses’
Full text linkIn this Reply, we discuss the differences between physical parameters used in the derivation of the Krausser-Samwer-Zaccone model of viscosity and those used in the justification of the empirical power-density scaling for repulsive power-law fluids. These fundamental differences preclude a direct combination of the two approaches
Amorphization of the intermetallic compound V2Zr by ball milling
No full textAmorphization of the intermetallic compound V2Zr by ball milling / Ulrich Herr and Konrad Samwer. - In: Journal of non-crystalline solids. 156-158. 1993. S. 608-61
Concentration dependence of the Debye temperature in extended solid solutions near the crystal-to-glass transition
No full textConcentration dependence of the Debye temperature in extended solid solutions near the crystal-to-glass transition / Christoph Ettl and Konrad Samwer. - In: Journal of non-crystalline solids. 156-158. 1993. S. 502-50
Local atomic order of a metallic glass made visible by scanning tunneling microscopy
No full textAbstract Exploring the atomic level structure in amorphous materials by STM becomes extremely difficult due to the localized electronic states. Here we carried out STM studies on a quasi-low-dimensional film of metallic glass Zr65Cu27.5Al7.5 which is ‘ultrathin’ compared with the localization length and/or the length scale of short range order. The local electronic structure must appear more inherent, having states at Ef available for tip-sample tunneling current. To enhance imaging contrasts between long-range and short-range orders, the highly oriented pyrolytic graphite was chosen as substrate, so that the structural heterogeneity arising from competition between the glass former ability and the epitaxy can be ascertained. A chemical order predicted for this system was observed in atomic ordered regimes (1–2 monolayers), accompanied with a superstructure with the period Zr–Cu(Al)–Zr along three hexagonal axes. The result implies a chemical short range order in disordered regimes, where polyhedral clusters are dominant with the solute atom Cu(Al) in the center. An attempt for the structural modelling was made based on high resolution STM images, giving icosahedral order on the surface and different Voronoi clusters in 3D space
Kolossaler Magnetowiderstand in Perowskitsystemen: ein Metall-Isolator-Übergang im Magnetfeld
No full textKolossaler Magnetowiderstand in Perowskitsystemen : e. Metall-Isolator-Übergang im Magnetfeld / Konrad Samwer ; Rittmar von Helmolt. - In: Festschrift zum Einzug in das neue Gebäude, Naturwissenschaften II, 1. Bauabschnitt, und zum Festakt am 15. Juli 1996. - Augsburg, 1996. - S. 83-8
Polaronic Emergent Phases in Manganite-based Heterostructures
No full textTransition metal functional oxides, e.g., perovskite manganites, with strong electron, spin and lattice correlations, are well-known for different phase transitions and field-induced colossal effects at the phase transition. Recently, the interfaces between dissimilar perovskites were shown to be a promising concept for the search of emerging phases with novel functionalities. We demonstrate that the properties of manganite films are effectively controlled by low dimensional emerging phases at intrinsic and extrinsic interfaces and appeared as a result of symmetry breaking. The examples include correlated Jahn–Teller polarons in the phase-separated (La1−yPry)0.7Ca0.3MnO3, electron-rich Jahn–Teller-distorted surface or “dead” layer in La0.7Sr0.3MnO3, electric-field-induced healing of “dead” layer as an origin of resistance switching effect, and high-TC ferromagnetic emerging phase at the SrMnO3/LaMnO3 interface in superlattices. These 2D polaronic phases with short-range electron, spin, and lattice reconstructions could be extremely sensitive to external fields, thus, providing a rational explanation of colossal effects in perovskite manganites
Fragility and thermal expansion control crystal melting and the glass transition
No full textAnalytical relations for the glass transition temperature, Tg, and the crystal melting temperature, Tm, are developed on the basis of nonaffine lattice dynamics. The proposed relations explain the following: (i) the seemingly universal factor of ≈2/3 difference between the glass transition temperature and the melting temperature of the corresponding crystal, and (ii) the recent empirical discovery that both Tg and Tm are proportional to the liquid fragility m divided by the thermal expansion coefficient α of the solid.HORIZON EUROPE European Research Council 10.13039/100019180Army Research Office 10.13039/10000018
Ultrafast heating of metallic glasses reveals disordering of the amorphous structure
No full textStudies of the transition from the supercooled liquid into the high temperature liquid of a glass formingmetal is commonly hindered by incipient crystallization processes. In this contribution we show that ametallic glass exhibits a significant sudden increase in the specific heat while crossing the transition fromthe supercooled liquid into the high temperature liquid without crystallizing. At this increase, hightemporal resolution X-ray studies show that the liquid structure changes and the crystallization behavioralso deviates from the common Zr(Cu,Al)-phase formation. We associate the increase in specific heatcapacity with the disordering of the amorphous structure like a scenario of a first order liquideliquidphase transition
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