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[en] Dimethylammonium copper (II) chloride (also known as DMACuCl3 or MCCL) is a low dimensional S=12 quantum spin system proposed to be an alternating ferro-antiferromagnetic chain with similar magnitude ferromagnetic (FM) and antiferromagnetic (AFM) exchange interactions. Subsequently, it was shown that the existing bulk measurements could be adequately modeled by considering DMACuCl3 as independent AFM and FM dimer spin pairs. We present here new inelastic neutron scattering measurements of the spin excitations in single crystals of DMACuCl3. These results show significant quasi-one-dimensional coupling, however the magnetic excitations do not propagate along the expected direction. We observe a band of excitations with a gap of Δ=0.95 MeV and a bandwidth of 0.82 MeV
[en] Zero field (ZF) and transverse field (TF) muon spin relaxtion and rotation (μSR) experiments have been carried out in the Cd-doped heavy fermion super conductor CeCoIn5 to investigate its superconducting state.
[en] A Green's function formalism is used to calculate the energy of impurity modes associated with one and/or two magnetic impurities in the one-dimensional Heisenberg XXZ magnetic chain. The system can be tuned from the Heisenberg to the Ising model varying a parameter λ. A numerical study is performed showing two types of localized modes (s and p). The modes depend on λ and the degeneracy of the acoustic modes is broken.
[en] In this study a comparison is made between the optical and electrical properties of Ni/Au and Ni/Ir/Au Schottky photodiodes based on Al0.35Ga0.65N. The effects of inserting Ir between Ni and Au are of particular interest. The comparison in the properties is done after annealing the photodiodes at different temperatures in an argon gas ambient. The reverse current decreased with annealing temperature up to 400 °C for the Ni/Au Schottky photodiode and up to 500 °C for the Ni/Ir/Au photodiode. The Schottky barrier heights increased with increasing annealing temperature. The responsivity of the Ni/Au photodiode was higher than that of the Ni/Ir/Au photodiode. The transmission of the Ni/Au metal layer improved with increasing annealing temperature up to 500 °C and the best transmission of the Ni/Ir/Au metal layer was after 400 °C annealing.
[en] SrAl2O4:Ce3+ phosphors were synthesized using the solution combustion method at a temperature of 500 °C. The Ce3+ ion concentration was varied from 0.25 to 2 mol%. X-ray powder diffraction (XRD) patterns exhibited the same main peaks for the lower dopant concentrations of Ce3+, and the average crystallite size was between 40 nm and 43 nm. The SrAl2O4:Ce3+ included a monoclinic phase. Scanning electron microscopy images revealed agglomerated particles as well as plate-like particles. Photoluminescence results demonstrated that the intensity decreased for Ce3+ concentrations up to 1 mol% and then increased again due to the formation of a second phase Sr3Al2O6. The emission peaks for the different concentrations of Ce3+ consists of two peaks situated at 356 nm and 380 nm corresponding to the 2F7/2 and 2F5/2 transitions.
[en] A systematic study of the influences of P content and CoP layer thickness on the magnetic properties and giant magneto-impedance (GMI) effect in electrodeposited CoP/Cu composite wires has been conducted. The results obtained show that there is a correlation between the structure, soft magnetic properties, and GMI effect in the wires. Among the compositions investigated, the optimized magnetic properties (i.e. the lowest coercivity) and the largest GMI ratio are achieved in Co85P15/Cu wires derived from an electrolyte containing H3PO3 concentration of 30 g/l with a plating duration of 3 min and a current density of 750 mA/cm2.
[en] ZnO micro-tetrapod microstructures were fabricated by a vapor phase transport method. Under the excitation of 325 nm continuous wave He–Cd laser, the microphotoluminescence spectrum from a single ZnO micro-tetrapod presented a two-band structure with a series of optical resonance modes; a possible optical resonance loop formed in two adjacent legs of the tetrapod was suggested, and the two-band spectrum structure was attributed to the exciton–exciton scattering process. The lasing emission was obtained from single ZnO micro-tetrapod under intense excitation of 355 nm nanosecond pulsed laser. The lasing spectrum shows clear mode structure with the lasing quality factor of 1300 and the lasing threshold of 150 kW/cm2. The microphotoluminescence resonance and lasing results indicate that ZnO tetrapod can serve as a high-Q ultraviolet microcavity laser.
[en] We study thermal quantum discord (TQD) in the Heisenberg chain with spin site or magnetic impurity. The former one of which may induce inhomogeneous exchange interactions between the neighboring spins, while the latter one may model a spin chain with nonuniform magnetic field. In contrast to one's traditional understanding, we found that the spin impurity can be used to enhance the TQD greatly for all the bipartition schemes of the chain, while the magnetic impurity located on one spin can make the TQD between the other two spins approaching its maximum 1 for the antiferromagnetic chain.