Enhanced functionality in magnonics by domain walls and inhomogeneous spin configurations

This paper discusses nanomagnetic structures enabling the manipulation of propagating spin waves. We address in particular how domain walls, or more generally speaking inhomogeneous spin configurations, enhance the control of spin-wave transmission and thereby the functionality of magnonic devices. Three different microscopic mechanisms are outlined, considering an interference device, a spin-wave bus and a magnonic crystal. Inhomogeneous spin configurations are argued to shift the spin-wave phase, guide spin waves in nanochannels and allow for reprogrammable spin-wave band structures in periodic nanostructures, respectively. Such devices and functionalities are relevant for further developments in magnonics.     

Masked auditory thresholds in three species of birds, as measured by the auditory brainstem response (L)

Auditory brainstem responses (ABRs) were recorded in adult budgerigars, canaries, and zebra finches in quiet and in three levels of white noise for tone stimuli between 1 and 4 kHz. Similar to behavioral results, masked ABR thresholds increased linearly with increasing noise levels. When the three species are considered together, ABR-derived CRs were higher than behavioral CRs by 18-23 dB between 2 and 4 kHz and by about 30 dB at 1 kHz. This study clarifies the utility of using ABRs for estimating masked auditory thresholds in natural environmental noises in species that cannot be tested behaviorally.     

Continuous wave 1.6 μm laser action in Er doped garnets at room temperature⋆

We report on room-temperature cw laser action of Er³⁺: Yttrium-aluminum-garnet (YAG) and Er³⁺: Yttrium-gallium-garnet (YGG) crystals at 1.64 m. The laser operates from the metastable⁴ I _13/2 manifold into an upper Stark level of the⁴ I _15/2 ground-state manifold of Er³⁺. Due to reabsorption losses, the Er³⁺ concentration of the laser crystals must be low. Laser pumping at a wavelength of 647.1 nm yields lowest thresholds around 30 mW and slope efficiencies up to 12.7% for Er:YAG. Laser operation in Er:YGG is achieved with higher thresholds of about 200 mW and smaller slope efficiencies of 0.9%. The effective emission cross section in YAG is estimated to be _e5×10^–21 cm².Dedicated to Prof. Dr. Herbert Welling on the occasion of his 60th birthday     

Revealing Bell’s nonlocality for unstable systems in high energy physics

Entanglement and its consequences—in particular the violation of Bell inequalities, which defies our concepts of realism and locality—have been proven to play key roles in Nature by many experiments for various quantum systems. Entanglement can also be found in systems not consisting of ordinary matter and light, i.e. in massive meson–antimeson systems. Bell inequalities have been discussed for these systems, but up to date no direct experimental test to conclusively exclude local realism was found. This mainly stems from the fact that one only has access to a restricted class of observables and that these systems are also decaying. In this Letter we put forward a Bell inequality for unstable systems which can be tested at accelerator facilities with current technology. Herewith, the long awaited proof that such systems at different energy scales can reveal the sophisticated “dynamical” nonlocal feature of Nature in a direct experiment gets feasible. Moreover, the role of entanglement and CP\mathcal{CP} violation, an asymmetry between matter and antimatter, is explored, a special feature offered only by these meson–antimeson systems.     

Phase transitions,ferroelectric behavior and second-order nonlinear optics of a new mixed sodium dihydrogen phosphate–arsenate

Aiming at the development of new proton conducting solids, recent studies of the NaH₂PO₄·H₂O–NaH₂AsO₄·H₂O system have lead to the synthesis of a new compound NaH₂(PO₄)_0.48(AsO₄)_0.52·H₂O (NDAP). Calorimetric studies have confirmed the presence of four reversible phase transitions (abbreviated by PhT), at 257/270 (PhT, IV), 261/290 (PhT, III), 267/301 (PhT, II) and 317/317.5 K (PhT, I) (for cooling/heating processes, respectively). It is shown that the III and IV phase transitions are of a first order type, with a “order-disorder and displacive” character, accompanied by specific dielectric anomalies. The behavior of the dielectric constant ε′_r and of tan δ shows that, at 272 K, the (PhT, IV) could be ferroelectric–paraelectric. As for the (PhT, III) at 296 K, it leads to a superionic–protonic phase; a jump in the conductivity is associated to this transition with an unusual high value of conductivity 1.07×10^?4 Ω^?1 cm^?1 and a low activation energy 0.39 eV (Kh. Jarraya et al.). Quandratic nonlinear (NLO) properties of NDAP powder was confirmed efficiency of the grown crystal by the Kurtz and Perry second harmonic generation (SHG) technique.     

Excellent passivation of thin silicon wafers by HF‐free hydrogen plasma etching using an industrial ICPECVD tool

In this work, hydrogen plasma etching of surface oxides was successfully accomplished on thin (～100 µm) planar n‐type Czochralski silicon wafers prior to intrinsic hydrogenated amorphous silicon [a‐Si:H(i)] deposition for heterojunction solar cells, using an industrial inductively coupled plasma‐enhanced chemical vapour deposition (ICPECVD) platform. The plasma etching process is intended as a dry alternative to the conventional wet‐chemical hydrofluoric acid (HF) dip for solar cell processing. After symmetrical deposition of an a‐Si:H(i) passivation layer, high effective carrier lifetimes of up to 3.7 ms are obtained, which are equivalent to effective surface recombination velocities of 1.3 cm s^–1 and an implied open‐circuit voltage (V_oc) of 741 mV. The passivation quality is excellent and comparable to other high quality a‐Si:H(i) passivation. High‐resolution transmission electron microscopy shows evidence of plasma‐silicon interactions and a sub‐nanometre interfacial layer. Using electron energy‐loss spectroscopy, this layer is further investigated and confirmed to be hydrogenated suboxide layers. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Composition of oxygen precipitates in Czochralski silicon wafers investigated by STEM with EDX/EELS and FTIR spectroscopy

In this work, we investigated the stoichiometry of oxygen precipitates in Czochralski silicon wafers. The thickness dependence of the Cliff–Lorimer sensitivity factor for the silicon/oxygen system was determined and applied for the investigation of the stoichiometry of oxygen precipitates by EDX. The results show that both plate‐like oxygen precipitates and a transitional form between plate‐like and octahedral precipi‐ tates consist of SiO₂. This was confirmed by EELS low loss spectra where the typical spectrum for amorphous SiO₂ was observed. Moreover, the absorption band of plate‐like precipitates at 1227 cm^–1 was found in the low temperature FTIR spectrum. It was demonstrated that this band can only be simulated by the dielectric constants of amorphous SiO₂. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)