Modern Physics Letters B

In this paper, crystal and magnetic properties of proton irradiated giant magnetoresistance spin valves (GMR-SVs) were investigated based on Ta/NiFe/CoFe/Cu/CoFe/IrMn/Ta stack. GMR-SVs were fabricated by magnetron sputtering and irradiated by 5 MeV proton energy. After irradiation, the magnetic phase of GMR-SV core structures was not affected distinctly while the crystal structure of Ta changed with the radiation dose and dose rate. Degradation of the saturated magnetization and the magnetoresistance ratio was shown in the proton-irradiated samples from the magnetization hysteresis curves and the magnetoresistance measurements, which was explained from the change in the zero-field resistance and the exchange interaction.

Electron subsystem of ultrathin films was analyzed using Green's function method including quantum size effect and effect of boundaries on Hamiltonian parameters. We have calculated basic physical properties of electrons in crystalline films: energy spectra, possible states, space distribution of electrons and the position of Fermi level, which enabled the complete insight into the thermodynamic or conducting characteristics of observed film-structure. The comparison with crystal bulk have shown that electronic properties of the materials are strongly influenced by both the sample dimensions and boundary conditions. The numerical calculations performed for very thin crystalline metallic-like films show that localized states and spatial distribution of the (quasi)free electrons might be manipulated by varying the surface parameters which is significant for operation of devices based on thin films.

In this paper, we theoretically analyze the electromagnetic properties of a negative refractive index medium configured as a four-level system under thermal bath effect. For different thermal bath coupling strengths, the system shows negative permittivity and permeability as well as a large negative refractive index. This atomic medium is stable against environmental effect in a large experimental reachable domain of parameters which makes it a potential candidate for important applications.

In this paper, we have numerically investigated a novel kind of ultra-compact wavelength demultiplexing (WDM) in high-confined metal–insulator–metal (MIM) plasmonic waveguides. It is found that the drop transmission efficiency of the filtering cavity can be strongly enhanced by introducing a side-coupled cavity in the MIM waveguide. The theoretical analysis is verified by the finite-difference time-domain simulations. Through cascading the filtering units, a highly effective triple-wavelength demultiplexer is proposed by selecting the specific separation between the two coupled cavities of filtering units. Our results may find potential applications for the nanoscale WDM systems in highly integrated optical circuits and networks.

In this paper, we study on breathers of Bose–Einstein condensate analytically in a time-dependent parabolic trap with a complex potential. It is found that the breather can be reflected by the parabolic potential or split into many humps and valleys with the time evolution. The nonlinear tunneling behavior of breather colliding on the parabolic potential is observed. The results provide many possibilities to manipulate breather experimentally in the condensate system.

In this paper, the influence of the spin-relaxation on the optical bistability via a nonradiative coherence between the heavy-hole and the light-hole in a GaAs quantum well inside a unidirectional ring cavity is studied. In the present theoretical model, spin-relaxation was considered as a source for decoherence and it was found that the spin-relaxation leads to the change of optical bistability behavior, including increase in threshold intensity and hysteresis loop. Furthermore, in the presence of spin-relaxation, the transition from optical bistability to optical multistability can be obtained by tuning the applied field.

In this paper, the momentum-resolved radio-frequency spectra of a unitary Fermi gas in the normal phase are presented and analyzed on the basis of the framework of the non-self-consistent T-matrix approximation with the extended Gorkov and Melik-Barkhudarov (GMB) approximation. We report the calculated occupied spectral intensity and energy distribution curves for different temperatures above T_c. Our results indicate the existence of pseudogap phenomenon which would be helpful for further understanding of the pseudogap in high-temperature superconductivity.

In this paper, we investigate the Landau and Baliaev damping of the collective modes in a two-component Bose gas using the mean-field approximation. We show that due to the two body atom–atom interaction, oscillations of each component is coupled to the thermal excitations of the other component which gives rise to creation or destruction of the elementary excitations that can take place in the two separate components. In addition, we find that the damping is also enhanced due to inter-component coupling.

A bipolar RRAM device based on Ni/HfO₂/n⁺-Si structure with self-rectifying characteristics is demonstrated for high density cross-bar memory application. Experimental results indicate that Ni conductive filament generated at LRS plays an important role in resistive switching, resulting in the formation of a Schottky junction at the Ni-CF/n⁺-Si interface which determines the self-rectifying behavior at LRS. These results are very important from the point of view of understanding the self-rectifying switching mechanism and improving the resistive switching characteristics of self-rectifying RRAM devices.

In this paper, we present a first principle investigation on Fe-doped GaN with wurtzite and zinc-blend structure using full potential density functional calculations. Data point out that the magnetic behavior of Fe-doped GaN system is strongly dependent on Fe doping configurations. In agreement with the experimental reports, and independently by doping, antiferromagnetism occurs in the zinc-blend structure, while in the wurtzite structure ferromagnetism depends on the Fe doping configurations. Detailed analyses combined with density of state calculations support the assignment that the ferromagnetism is closely related to the impurity band at the origin of the hybridization of Fe 3d and N 2p states in the Fe-doped GaN of wurtzite phase.