Materials Literature
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Intermetallic YCo2 compound is a Pauli exchange-enhanced paramagnet. Structural and magnetic properties melt-spun YCo2 pure and alloyed with Nb or Ti are presented. The samples crystallize in MgCu2-type phase with lattice constant a changing from 7.223 Å for YCo2, through 7.213 Å for Y0.9Nb0.1Co2 to 7.192 Å for Y0.9Ti…
Crystal and magnetic structures of the x = 0.2 member of the La0.8-xTbxCa0.2CoO3 perovskite series have been determined from powder neutron diffraction. Enhancement of the diffraction peaks due to ferromagnetic or cluster glass ordering is observed below TC = 55 K. The moments first evolve on Co sites, and ordering of…
We report on the magnetic entropy change and the critical exponents in the double perovskite manganite Y2NiMnO6 with a ferromagnetic to paramagnetic transition TC=85K. For a magnetic field change of 80kOe, a maximum magnetic entropy change -6.57 J /kg K is recorded around TC. The corresponding relative cooling power (…
Strong modification of spontaneous emission of Eu3+ ions placed in close vicinity to thin and thick gold and silver films was clearly demonstrated in a microscope setup separately for electric and magnetic dipole transitions. We have shown that the magnetic transition was very sensitive to the thickness of the gold su…
The switching of the magnetic configuration of giant magnetoresistance multilayers not only changes the electrical and thermal conductivities but also the thermopower. We study the magnetotransport and the magnetothermoelectric properties of Co/Cu multilayer devices in a lateral thermal gradient. The Seebeck coefficie…
We apply ultrafast x-ray diffraction with femtosecond temporal resolution to monitor the lattice dynamics in a thin film of multiferroic BiFeO3 after above-band-gap photoexcitation. The sound-velocity limited evolution of the observed lattice strains indicates a quasi-instantaneous photoinduced stress which decays on…
With nearly complete spin polarization, the ferromagnetic semiconductor europium monoxide could enable next-generation spintronic devices by providing efficient ohmic spin injection into silicon. Spin injection is greatly affected by the quality of the interface between the injector and silicon. Here, we use atomic-re…
We study the dynamics of head-to-head domain walls separating in-plane domains in a disordered ferromagnetic thin film. The competition between the domain-wall surface tension and dipolar interactions induces a crossover between a rough domain-wall phase at short length scales and a large-scale phase where the walls d…
Heavy metals in high concentrations can cause health and environmental damage. Nanosilver is an emerging heavy metal which has a bright future of use in many applications. Here we report on the levels of silver and other heavy metals in municipal sewage sludge. Five towns in Limpopo province of South Africa were selec…
We report a facile in situ synthesis of reduced graphene oxide (RGO)-phenol formaldehyde (PF) composites with an interactive oxidation-reduction reaction. In this interactive chemical reaction, graphene oxide (GO) was reduced to RGO by phenol, and simultaneously phenol was oxidized to benzoquinone. The noncovalently a…
Sulfur-doped polyimide (SPI) photocatalysts were synthesized for the first time via an in situ thermal copolymerization method using sublimed sulfur (S4) as a dopant. Sulfur doping not only extended the absorption range of polyimide (PI) for visible light but also enhanced the oxidation ability of the photoinduced hol…
Structural rearrangement of liquid Bi in the vicinity of the melting point has been proposed due to the unique temperature invariant sound velocity observed above the melting temperature, the low symmetry of Bi in the solid phase and the necessity of overheating to achieve supercooling. The existence of this structura…
We present a method for the first-principles calculation of nuclear magnetic resonance (NMR) J-coupling in extended systems using state-of-the-art ultrasoft pseudopotentials and including scalar-relativistic effects. The use of ultrasoft pseudopotentials is allowed by extending the projector augmented wave (PAW) metho…
Two-dimensional electron gases (2DEGs) at oxide heterostructures are attracting considerable attention, as these might one day substitute conventional semiconductors at least for some functionalities. Here we present a minimal setup for such a 2DEG--the SrTiO3(110)-(4 × 1) surface, natively terminated with one monolay…
In a theoretical study we investigate the electronic structure and band gap of the inverse spinel ferrite NiFe2O4. The experimental optical absorption spectrum is accurately reproduced by fitting the Tran-Blaha parameter in the modified Becke-Johnson potential. The accuracy of the commonly applied Tauc plot to find th…
Large-area bilayer graphene (BG) is grown epitaxially on Ru(0001) surface and characterized by low temperature scanning tunneling microscopy. The lattice of the bottom layer of BG is stretched by 1.2%, while strain is absent from the top layer. The lattice mismatch between the two layers leads to the formation of a mo…
We investigate thermoelectric effects in quantum well systems. Using the scattering approach for coherent conductors, we calculate the thermocurrent and thermopower both in the spin-degenerate case and in the presence of giant Zeeman splitting due to magnetic interactions in the quantum well. We find that the thermoel…
A(1-x)Fe(2-y)Se2 (A = K, Cs, Rb, Tl) are recently discovered iron-based superconductors with critical temperatures (Tc) ranging up to 32 K. Their parent phases have unique properties compared with other iron-based superconductors; e.g., their crystal structures include ordered Fe vacancies, their normal states are ant…
The lattice dynamics of the metallic tin β and γ polymorphs has been studied by a combination of diffuse scattering, inelastic x-ray scattering and density functional perturbation theory. The non-symmorphic space group of the β-tin structure results in unusual asymmetry of thermal diffuse scattering. Strong resemblanc…
We examine the PT-symmetry-breaking transition for a magnetic metamaterial of a finite extent, modeled as an array of coupled split-ring resonators in the equivalent circuit model approximation. Small-size arrays are solved completely in closed form, while for arrays larger than N=5 results were computed numerically f…