Hyperfine interactions of polarized β-emitting12B and12N in Si,Ge, and GaP

Using a nuclear reaction, the polarized short-lived -emitters¹²B and¹²N were implanted into Si, Ge, and GaP crystals. Hyperfine fields were studied via both NMR techniques and an external magnetic holding field H_ext on-off techniques in an H_ext range 0–8 kG and a temperature range 100–1000 K. No significant NMR signal was observed between 2 and 30 MHz for¹²N in Si and Ge despite maintenance of 60% polarization at T100 K and H_ext>4 kG, whereas for¹²B in Si at T>800 K almost full polarization was found at the Larmor frequency.     

Theory of metal–insulator transition in PrFe4P12 and PrRu4P12

We derive all symmetry allowed couplings between Fe/Ru or P ion displacements and the Pr ion 4f² ground state doublet in PrFe₄P₁₂ and PrRu₄P₁₂. A (1,1,−2)-type distortion of the Fe/Ru positions splits the 4f² doublet into non-magnetic eigenstates with opposite quadrupole moments. The sign of both the distortion and the quadrupole moment alternate from site to site, resulting in anti-quadrupolar ordering. A (1,1,1)-type distortion does not lift the degeneracy of the 4f² doublet. Either distortion may also open a gap at the Fermi surface, causing a metal–insulator transition in PrRu₄P₁₂ and a partial metal–insulator transition in PrFe₄P₁₂.     

π0-production in12C+12C at 800 and 1000 MeV/u

⁰-production in the system¹²C+¹²C was studied with the two-arm photon spectrometer TAPS at projectile energies of 800 and 1000 MeV/u. The experiments focus on the determination of the cross sections and the correspondingp _t -distributions. The results will extend the existing systematics of ⁰-production in heavy-ion collisions to a system with small mass.Presented at the International School-Workshop Relativistic Heavy-Ion Physics, Prague (Czech Republic), 19–23 September 1994.     

Sound Velocity and Release Behaviour of Shock-Compressed LY12 Al

A velocity interferometer system for any reflector (VISAR) is used to measure the sound velocity of LY12 Al shock-compressed to peak pressures of 20, 32, 55 and 71 GPa. Unloading wave velocities from these pressures are obtained from the observed particle velocity profiles at the LY12 Al/LiF window interface; and the longitudinal, bulk and shear sound velocities at the initial Hugoniot state are well determined. The histories of stress, strain, density or volume, and particle velocity along the release paths are calculated by the impedance-matching method based on the unloading sound velocity data. It is revealed that the re/ease behaviour of shocked LY12 Al departures obviously from the elastic perfectly-plastic response.     

Electron scattering with the excitation of the 15.11 MeV state of12C and theπ 12B12C coupling constant

Theπ ¹²B¹²C coupling constant is extracted from the data on theM1 form factor of¹²C using the PCAC and CVC hypotheses. The extrapolation of the form factor to the pion pole using analyticity arguments leads to the value \(f_{\pi ^{12} B^{12} C}^2 = 0.052\) . Our present knowledge of this coupling constant is discussed.     

Wetting and reaction promoted by ultrasound between sapphire and liquid Al–12Si alloy

Ultrasonic-assisted wetting between sapphire bulks and liquid Al–12Si alloy in an atmospheric environment at 620 °C is carried out in this study. Complete, rather than partial, wetting and joining can be achieved with the aid of ultrasound. Growth of epitaxial alumina on sapphire bulks is promoted dramatically during ultrasonic-assisted wetting comparing to that during hot-dipping without ultrasound. XRD results show that the epitaxial alumina is non-crystalline. This indicates that the temperature on the surface of the sapphire substrate is not more than 1200 °C even though the collapse of acoustic cavitation bubbles could theoretically produce extremely high temperature. The bonding force at the interface between the Al–Si alloy and sapphire is strengthened because of the epitaxial alumina. The interfacial shear strength of sapphire/Al–Si alloy can reach as high as 60–65 MPa. The fracture morphology shows that cracks initiated at the interface between Si grains and the epitaxial alumina on sapphire. This result is especially useful for the joining of metals and ceramics.     

Three-alpha force and the 3-α model of12C

We postulate a Gaussian three-body potential amongα particles and adjust its parameters so that, when it is added to the Ali-Bodmerα-α potential, a good fit to experimental energies of low-lying 0⁺ and 2⁺ states of¹²C is achieved. With these potentials we made a linear variational calculation in a basis of harmonic oscillator functions which are translationally invariant, completely symmetric, and have a definite orbital angular momentum. We study the influence of this three-body potential on elastic and inelastic form factors, transition widths, Coulomb energy and charge radius of the 3-α system. The 3-α potential improved results found with the Ali-Bodmer potential alone. We find the 0 ₂ ⁺ state to be a (non-rigid) linear chain and the ground state to be a triangle ofα particles.     

Measurement of Gamma-Rays from 11ΛB and 12ΛC

From the ^12 C（π^＋,K^＋）^12 AC reaction the γ -rays of 261.6±0.24 ke V（7/2^＋ →5/2^＋）and 1481.7±0.7 ke V（1/2^＋ →5/2^＋） of ^11 A B,and 2667.3±2.8 keV（1^- 2 → 2^- 1）of ^12 A C hypernuclei have been identified using a large germanium detector array Hyperball2 at K6 beam line of KEK. The observed energies of the transitions 1481.7keV and 261.6 keV are significantly different from the values predicted by the shell model using the △ and SN parameters determined from the ^7 △ Li data.     

Magnetic Properties of Melted ThMn12-Type Carbides and Their Nitrides

The carbides of NdDy0.2Fe12-yMoyC0.6 （y = 1.5, 2） crystallized in the ThMn12-type structure have been successfully synthesized by arc melting method, followed by a heat treatment. The magnetic properties are strongly enhanced with the addition of carbon. Upon the carbonation the saturation magnetization Ms is increased by about 20emu/g and the Curie temperature Tc is enhanced by 40-70K. The spin reorientation （SR） temperature decreases from 125 K for NdDy0.2Fe10Mo2 to 55 K for NdDy0.2Fe10MO2C0.6 indicating the change of magnetocrystalline anisotropy in the Nd sublattice. It is found that the intrinsic magnetic properties of the carbides can be improved by further nitrogenation, The composite carbon-nitrogen compounds show a Tc - 560K, M8 - 105 emu/g and Ha （anisotropy field） - 86kOe for NdDy0.2Fe10Mo2Co.6Nz and a Tc- 628K, M8 - 119 emu/g and Ha - 115kOe for NdDy0.2Fe10.5Mo1.5C0.6Nz. These magnetic properties are even better than those of simple nitrides, suggesting that these compounds can be considered as a good candidate for permanent magnet applications.     

High resolution infrared and Raman spectroscopy of ν 2 and associated combination and hot bands of 13C12CD2

Infrared and Raman spectra of dideuterated acetylene containing one ¹³C atom, ¹³C¹²CD₂, have been recorded and analysed to obtain detailed information on the fundamental ν ₂ band and associated combination and hot bands. Infrared spectra were recorded at 4?×?10^?3?cm^?1 resolution in the region 1150?2900^?cm^?1, which contains combination and hot bands from the ground and the bending v ₄?=?1 and v ₅?=?1 states. The Q-branches of the ν ₂ fundamental and associated hot bands (ν ₂?+?ν ₄???ν ₄, ν ₂?+?ν ₅???ν ₅, ν ₂?+?2ν ₄???2ν ₄, ν ₂?+?2ν ₅???2ν ₅ and ν ₂?+?ν ₄?+?ν ₅???(ν ₄?+?ν ₅)) were recorded using inverse Raman spectroscopy, with an instrumental resolution of about 3?×?10^?3?cm^?1. In addition, the observation of the 2ν ₂???ν ₂ Raman band was carried out populating the v ₂?=?1 state by stimulated Raman pumping. In total, 11 Raman and 9 infrared bands were analysed, involving all the l-vibrational components of the excited stretching?bending manifolds up to v _t ?=?v ₄?+?v ₅?=?2.

A simultaneous analysis of all infrared and Raman assigned transitions has been performed on the basis of a theoretical model which takes into account the rotation and vibration l-type resonances within each vibrational manifold and the Darling?Dennison anharmonic resonance between the ν ₂?+?2ν ₄ and ν ₂?+?2ν ₅ states. The parameters obtained reproduce the assigned transition wavenumbers with a standard deviation of the same order of magnitude as the experimental uncertainty.     

SrCoxZrxFe12−2xO19 and SrNixZrxFe12−2xO19 hexaferrites: A Comparison Study of AC Susceptibility,FC-ZFC and hyperfine interactions

This study compares the AC susceptibility, FC-ZFC and hyperfine interactions of Sr(Co_xZr_x)Fe_12−2xO₁₉ and Sr(Ni_xZr_x)Fe_12−2xO₁₉ hexaferrites (HFs) manufactured via ultrasonic route. The formation of M-type hexaferrites have been confirmed by X-ray powder diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR) and high-resolution transmission electron microscopy (HR-TEM) techniques. Scanning electron microscopy (SEM) presented the hexagonal-platelet morphology of products. The variation in isomer shift, line width, quadrupole splitting and hyperfine magnetic field values of them have been governed by ⁵⁷Fe Mössbauer spectroscopy which showed that Co²⁺ and Zr⁴⁺ ions located at generally octahedral and 2b sites, while Ni²⁺ and Zr⁴⁺ ions located at octahedral 12k and 4f₂ sites. Measurements of magnetization versus temperature (M-T) and AC susceptibility versus temperature were carried out. The various synthesized HFs displayed ferrimagnetic behavior in the temperature interval of 10–325 K. Super-spin glass-like behavior was noticed at lower temperatures. Neel-Arrhenius and Vogel-Fulcher models were used to explore the experimental AC susceptibility. It was showed that a lower Co-Zr substitution content leads to strengthen the magnetic exchange interactions, however even low Ni-Zr substitution content provoke a reduction in magnetic exchange interactions.     

Electronic structure and magnetic and electromagnetic wave absorption properties of BaFe12-xCoxO19 M-type hexaferrites

Crystal, electronic structures and the magnetic and electromagnetic wave absorption properties of BaFe_12-xCo_xO₁₉ (x = 0–2) M-type hexaferrites prepared by a co-precipitation technique were studied. The analyses of X-ray diffraction patterns indicated that the samples mainly crystallized in the P6₃/mmc hexagonal structure, with the additional constitution of Y-type hexaferrite as x > 0. The replacement of Co²⁺ for Fe³⁺ in BaFe_12-xCo_xO₁₉ changed the lattice constants and caused lattice distortions. Particularly, Co²⁺ doping also reduced magnetization and hard magnetic property of BaFe_12-xCo_xO₁₉. This is ascribed to magnetic moment of Co²⁺ smaller than that of Fe³⁺ and to the decrease of magnetocrystalline anisotropy. Having studied electromagnetic wave absorption properties in the frequency range f = 0.1–18 GHz, we found BaFe_12-xCo_xO₁₉ showing high reflection loss (RL) values at frequencies of 0.1–15 GHz, but fairly low RL values at higher frequencies. These features suggest that BaFe_12-xCo_xO₁₉ can be suitable to electronic devices working at GHz frequencies.     

Dipolar Interaction and Magnetic Ordering Ground State in Mn12 Molecular Magnet

Here a direct calculation of the dipolar interaction in a single crystal Mn12, with all of Mn ions summed, shows that a transition between ferromagnetic and antiferromagnetic ground states takes place where the dimension along the α（b） axis versus the dimension along the c axis reaches a certain critical value. It is shown that the w ~ ~ ground state is dependent upon the shape of the specimen. The reason of the shape dependence of ordering is that dipolar interaction is of long-range nature and the sign of dipolar interaction is dependent on the direction.     

Hybrid Integration of 1 × 12 Metal-Semiconductor-Metal Photodetector and Polyimide Waveguide Array

We report here a demonstration of hybrid integration of a 1 × 12 metal-semiconductor-metal (MSM) photodetector array and polyimide channel waveguides via 45° total-internal-reflection (TIR) micro-couplers. The two-layer polyimide waveguide array was constructed using Ultradel 9120D for the core and Ultradel 9020 for the lower cladding layer. The coupling loss and propagation loss of the waveguide are 0.2dB and 0.21 dB/cm, respectively. The cross talk of the adjacent channels is -32 dB. The MSM photodetector array was fabricated on a semi-insulated GaAs wafer. The photodetectors are integrated to operate in the conventional vertical illumination mode. We measured the external quantum-efficiency and 3 dB bandwidth of the integrated MSM photodetectors at 0.4 A/W and 2.648 GHz, respectively. The aggregate 3 dB bandwidth of the 12-channel integrated system is 32 GHz.     

Deposition of Er：A12O3 Films and Photoluminescence Characteristics

Er^3 -doped Al2O3 films were deposited on silicon substrates by reactive closed-field unbalanced magnetron sput-tering. The process parameters, such as target bias voltage, substrate bias voltage, O2 gas flows, sputtering gas pressure, were studied. The 1.53μm photoluminescence characteristics from Er^3 were measured. The relations among the PL peak intensity, annealing temperatures, and pump power were experimentally investigated.     

Crystal structure and ferroelectric property of Bi4Si3O12-added Bi4−xSmxTi3O12

We synthesized Bi_4?xSm_xTi₃O₁₂ (x=0.55, 0.65, 0.80) and y mol% Bi₄Si₃O₁₂-added Bi_4?xSm_xTi₃O₁₂ (x=0.65; y=5, 10, 15, 20) by a solid-state reaction, and investigated a relationship between the ferroelectric properties and crystal structures in these samples. From the P–E hysteresis measurements, it was clarified that the Bi_3.35Sm_0.65Ti₃O₁₂ showed better ferroelectric properties than the others with different Sm content, and the sample began to exhibit larger remanent polarization by adding Bi₄Si₃O₁₂. In order to examine an effect of the Bi₄Si₃O₁₂-addition from a structural point of view, we measured synchrotron X-ray diffractions of the samples at room temperature and 1000 K, and analyzed their crystal and electronic structures with the Rietveld technique and the maximum entropy method. As a result, it was suggested that the Bi₄Si₃O₁₂-addition made distortions of the Ti-O₆ octahedra larger and had an effect on the TiO bond strengths.     

17O12C17O and 18O12C17O spectroscopy in the 1.6 μm region

Near infrared spectra of a carbon dioxide sample enriched with oxygen-17 have been recorded using a high-resolution continuous scan Fourier transform interferometer fitted with a femto OPO/Idler laser source. Cavity enhanced absorption has been achieved in a static gas cell allowing an optimal rms noise equivalent absorption of 1.2?×?10^?10?cm^?1?Hz^?1/2 per spectral element to be reached, corresponding to α_min?=?10^?8?cm^?1. Spectra were calibrated against acetylene reference line positions. Three bands in the 3ν₁?+?ν₃ tetrad in both ¹²C¹⁷O₂ and ¹²C¹⁷O¹⁸O have been identified and rotationally analyzed, as well as some related hot bands, eight of which are newly reported and three with their analysis updated compared with a preliminary report (X. de Ghellinck d’Elseghem Vaernewijck et al., Chem. Phys. Lett. 514, 29 (2011)).     

121,123Sb and 75As NMR and NQR investigation of the tetrahedrite (Cu12Sb4S13) – Tennantite (Cu12As4S13) system and other metal arsenides

This work is motivated by the recent developments in online minerals analysis in the mining and minerals processing industry via nuclear quadrupole resonance (NQR). Here we describe a nuclear magnetic resonance (NMR) and NQR study of the minerals tennantite (Cu₁₂As₄S₁₃) and tetrahedrite (Cu₁₂ Sb₄S₁₃). In the first part NQR lines associated with ⁷⁵As in tennantite and ^121,123Sb isotopes in tetrahedrite are reported. The spectroscopy has been restricted to an ambient temperature studies in accord with typical industrial conditions. The second part of this contribution reports nuclear quadrupole-perturbed NMR findings on further, only partially characterised, metal arsenides. The findings enhance the detection capabilities of NQR based analysers for online measurement applications and may aid to control arsenic and antimony concentrations in metal processing stages.