Electromagnetic wave-absorption properties of rapidly quenched of Nd–Fe–B nanocomposites with low Nd content

The electromagnetic wave-absorption properties of Nd₃Fe_68−xMn_xCo₁₈B₁₁ (x=0, 1, 2) alloys obtained by rapid quenching from the melt was studied. The complex permittivity-frequency and permeability-frequency properties were determined in the microwave frequency regime of 2–18 GHz by vector network analysis. XRD spectra showed that only α-Fe diffraction peak was observed in the as-spun alloys. It is found that the acquired complex permittivity and permeability values match the microwave frequency when the 1 at% Mn content was doped. A minimum reflection loss of −6.9 dB is obtained at 2.7 GHz for composite Nd₃Fe₆₆Mn₂Co₁₈B₁₁ with absorber thickness of 1.5 mm. The exchange interaction was attributed to the microwave absorption properties. The results suggest a new design of microwave absorbers based on electromagnetic wave-absorbing materials.     

Magnetic properties of Nd3+ in Nd−Ba−Cu−O-compounds

Neutron diffraction, neutron spectroscopy and magnetization measurements have been employed to study the structural, electronic, and magnetic behavior of eleven compounds with the general formula Nd_1+y Ca _v Ba_2–y–v Cu₃O _x (0y0.5; 0v0.25; 6x7). The structure turned out to react to oxygen reduction similar as other 123-compounds, yielding discontinuities close to the metal-insulator-transition and the well-known relations of bond lengths as a function ofT _c. The crystalline electric field (CEF) interaction, splitting the 10-fold degenerate ground-state J-multiplet of the Nd³⁺-ions into five doublet states, was investigated by neutron spectroscopy. The derived CEF parameters have been used to determine changes in the electronic surroundings of the Nd³⁺ ions. In addition, with the help of the CEF parameters the thermodynamic magnetic properties of these compounds were calculated which turn out to be in good agreement with the experimental data.     

Comparative study of the mode-locking of Nd:GdVO_4 and Nd:YAG lasers with semiconductor saturable absorber mirrors

Stable continuous-wave passive mode-locking of diode-end-pumped Nd:GdVO4 and Nd:YAG lasers with semiconductor saturable absorber mirrors (SESAMs) are reported. The comparative study shows that the Nd:GdVO4 crystal is efficient to decrease the Q-switched mode-locking tendency, and easier to continuous-wave (CW) mode lock than Nd:YAG.     

Generic phase diagram of Nd2−xCexCuO4

We investigated the generic phase diagram of the electron doped superconductor, Nd_2?xCe_xCuO₄, using films prepared by metal organic decomposition. After careful oxygen reduction treatment to remove interstitial O_ap atoms, we found that the T_c increases monotonically from 24 K to 29 K with decreasing x from 0.15 to 0.00, demonstrating a quite different phase diagram from the previous bulk one. Based on the discussion on the tremendous influence of O_ap “impurities” on superconductivity in T′ cuprates, we conclude that our result represents the generic phase diagram for oxygen-stoichiometric Nd_2?xCe_xCuO₄.     

Effects of post-sinter annealing on microstructure and magnetic properties of Nd–Fe–B sintered magnets with Nd–Ga intergranular addition

We investigate the effects of post-sinter annealing on the microstructure and magnetic properties in B-lean Nd–Fe–B sintered magnets with different quantities of Nd–Ga intergranular additions. The magnet with fewer Nd–Ga additions can enhance 0.2 T in coercivity, with its remanences nearly unchanged after annealing. With the further increase of the Nd–Ga addition, the annealing process leads coercivity to increase 0.4 T, accompanied by a slight decrease of remanence. With the Nd–Ga addition further increasing and after annealing, however, the increase of coercivity is basically constant and the change of remanence is reduced. Microstructure observation indicates that the matrix grains are covered by continuous thin grain boundary phase in the magnets with an appropriate Nd–Ga concentration after the annealing process. However, the exceeding Nd–Ga addition brings out notable segregation of grain boundary phase, and prior formation of part RE6 Fe13 Ga phase in the sintered magnet. This prior formation results in a weaker change of remanence after the annealing process.Therefore, the diverse changes of magnetic properties with different Nd–Ga concentrations are based on the respective evolution of grain boundary after the annealing process.     

Laser Performance of Nd：GGG Operating at 938 nm

We report an efficient diode-pumped Nd-doped Gadolinium gailium garnet （GGG） continuous-wave （CW） laser operating at 938nm. Laser action of 1.6at.% Nd-doped GGG crystais with different lengths and temperatures are aiso investigated. The maximum output power of 620mW is obtained at the incident pump power of 5.0 W with a slope efficiency of 15%.     

Magnetic properties of Nd0.5Pb0.5-xSrxMnO3 materials

The structure and magnetic properties of Nd0.5Pb0.5-xSrxMnO3 (0≤x≤0.4) manganites were systematically investigated. Significant changes in Curie temperature and metal-insulator (MI) transition temperature of the samples were observed. All samples exhibited a transition from paramagnetic semiconducting to ferromagnetic metallic state.Curie temperature Tc and the MI transition temperature Tp increased with increasing Sr content. We attributed these behaviours to the enhancing of both the double exchange mechanism and the Jahn-Teller electron-phonon coupling.     

Continuous-wave diode-pumped laser action of Nd³⁺-doped photo-thermo-refractive glass

Laser action of the photo-thermo-refractive (PTR) glass, which is the photosensitive material for holographic recording of volume Bragg gratings (VBGs), was demonstrated for the first time by introducing Nd3?. Nd:PTR glass has a bandwidth of 27.8 nm and 16.0 nm for luminescence and absorption, respectively. An uncoated 2 mm thick Nd:PTR element generated cw laser output of 124 mW, with a slope efficiency of 25%, by laser diode pumping. This Nd:PTR glass also performed wide bandwidth laser action at 1053.9-1063.3 nm, where the decrease of the pump-absorption efficiency was held off below 30%, even under a 3.5 nm shift of pump wavelength from its absorption center.     

A comprehensive study of Nd:YAG, Nd:YAlO3, Nd:YVO4 and Nd:YGdVO4 lasers operating at wavelengths of 0.9 and 1.3 μm. Part 1: cw-operation

This paper reports on efficient generation of cw laser radiation at 0.9 and 1.3 μm in different neodymium doped laser hosts. The thermal, mechanical and optical properties as well as the laser performance of Nd:YAG, Nd:YAlO₃, Nd:YVO₄ and Nd:GdVO₄ are studied in numerical simulations as well as in experimental investigations. For example an output power of more than 4.0 W is generated in Nd:YVO₄ at the 914 nm ⁴F_3/2→⁴I_9/2 transition using a pump power of 19 W. In Nd:GdVO₄ more than 6.0 W are obtained at the 1342 nm ⁴F_3/2→⁴I_13/2 laser transition by using a pump power of 19.3 W. The spatial beam quality of both lasers is diffraction limited with an M² value of less than 1.1. PACS  42.70.Hj; 42.55.Xi; 42.60.Pk     

Decay of Nd140→Pr140→Ce140

An intermediate image magnetic spectrometer was used to study the continuous ⁺-spectrum of Pr¹⁴⁰ and the Auger electrons of the decay chain Nd¹⁴⁰Pr¹⁴⁰Ce¹⁴⁰. The maximum energy of the continuous ⁺-spectrum is 2318±10 keV. The ratio of the intensities of the different Auger groupsK–LLK–LXK–MX=1 (0.58±0.05) (0.09±0.02). The ratio of the number of Auger electrons of the K-series to the electrons of the continuous spectrume _K/ ⁺ is 0.292.

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Nd¹⁴⁰Pr¹⁴⁰Ce¹⁴⁰

Pr¹⁴⁰ Nd¹⁴⁰ Pr¹⁴⁰¹⁴⁰. ⁺- — 2318±10 keV. -:K–LLK–LXK–MX=1(0,58±0,05) (0,09±0,02). K e _K/ ⁺=0,292.

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We should like to thank Z. Macháek and Z. Dubcová for help in the measurements and J. Vlachý, graduate of the Faculty of Technical and Nuclear Physics, for help in the measurements and elaboration of the experimental results.     

The analysis of the transient temperature distribution of double-slab Nd:YAG laser medium

A novel double-slab Nd:YAG laser, which uses face-pumped slab medium cooled by liquid with different temperatures on both sides, is proposed. The thermal distortion of wavefront caused by the non-uniform temperature distribution in the laser gain media can be self-compensated. According to the method of operation, the models of the temperature distribution and stress are presented, and the analytic solutions for the model are derived. Furthermore, the numerical simulations with pulse pumping energy of 10 J and repetition frequencies of 500 and 1000 Hz are calculated respectively for Nd:YAG laser medium. The simulation results show that the temperature gradient remains the approximative linearity, and the heat stress is within the extreme range. Then the absorption coefficient is also discussed. The result indicates that the doping concentration cannot be too large for the high repetition frequency laser. It has been proved that the high repetition frequency, high laser beam quality, and high average outp     

Effects of oxidation of DyH_3 in Nd–Fe–B sintered magnets

The effects of oxidation of Dy H3 with respect to dysprosium addition to Nd–Fe–B sintered magnets are examined.Samples sintered with the addition of freshly milled dysprosium hydride, dysprosium hydride exposed to air at room temperature for 15 min and dysprosium hydride exposed to air at 100°C for 3.5 hours are studied from the aspects of magnetic properties, microstructures, and their degradation, respectively. It is found that some oxidized dysprosium is distributed in the Nd-rich phase; hence, the decrease of remanence occurred. The degradation results indicate that preoxidised dysprosium can be a major factor in increasing the corrosion rate. The microstructures and corrosion acceleration test suggested that the oxidation is detrimental to remanence.     

Properties of Nd：YAG Laser with the Nonlinear Absorption of the Intracavity Fullerenes

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Effect of Nd on the Superconductivity of Nd1+x Ba2-x Cu3O y with 0.1 ≤ x ≤ 0.35

The effect of Nd substitution at the Ba sites has been studied in Nd_1+x Ba_2-x Cu₃O _y system for 0.1 x 0.35. Orthorhombic to tetragonal structural phase transition occurs at about x = 0.17. With the increase of Nd, the T _c value decreases and T increases, where T is the difference between the onset and critical temperatures and indicates the sharpness of the transition. These changes are explained by ac-susceptibility measurements on Nd_1.1Ba_1.9Cu₃O_7.12 at 0.10 Oe. The susceptibility curves show the presence of about four phases, which are not detectable by X-ray diffraction technique.     

Comparison of laser performance of electro-optic Q-switched Nd:YAG ceramic/single crystal laser

An electro-optic Q-switched Nd:YAG ceramic laser operating at kHz repetition rate was demonstrated. Thermal induced lens' focus of ceramic rod was measured and compensated by plano-convex cavity structure. Depolarization loss at different output powers was measured in Nd:YAG single crystal and ceramic lasers. High-energy high-beam-quality laser pulse output was obtained in both laser structures. Pulse energy of about 20 mJ and pulse width of less than 12 ns were achieved, and the average power reached 20 W. The divergence of output laser beam was less than 1.2 mrad, and the beam propagation factor M2 was about 1.4.     

Characteristics of Nd：GdVO4 Laser with Different Nd-Doping Concentrations

We report the properties of a compact diode-pumped continuous-wave Nd：GdV04 laser with a linear cavity and different Nd-doped laser crystals. In a 0.2at.% Nd-doped Nd：GdVO4 laser, 1.54 W output laser power is achieved at 912nm wavelength with a slope efficiency of 24.8% at an absorbed pump power of 9.4W. With 0.3at.% Nd-doping concentration, we can obtain the either single-wavelength emission at 1064nm or 912nm or the dual-wavelength emission at 1064nm and 912nm by controlling the incident pump power. From an incident pump power of 11.6 W, the 1064nm emission between ^4Fa/2 and ^4I11/2 is suppressed completely by the 912nm emission between ^4Fa/2 and ^4I9/2. We obtain 670 mW output of the 912nm single-wavelength laser emission with a slope efficiency of 5.5% by taking an incident pump power of 18.4 W. Using a Nd：GdV04 laser with 0.4at.% Nd-doping concentration, we obtain either the single-wavelength emission at 1064nm or the dual-wavelength emission at both 1064nm and 912nm by increasing the incident pump power. We observe a strong competition process in the dualavelength laser.     

Pulsed Laser Characteristics of Nd∶GdCOB Crystal at 1331.0 nm

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Pulsed Laser Characteristics of Nd∶GdCOB Crystal at 1331.0nm

ＡｌａｒｇｅｓｉｚｅａｎｄｈｉｇｈｏｐｔｉｃａｌｑｕａｌｉｔｙＮｄ∶ＧｄＣＯＢｃｒｙｓｔａｌｗａｓｏｂｔａｉｎｅｄｂｙＣＺｐｕｌｌｉｎｇｍｅｔｈｏｄ.Ｔｈｅｃｒｙｓｔａｌｓｗｅｒｅｃｕｔｉｎｔｗｏｓａｍｐｌｅｗｉｔｈｔｈｅｓａｍｅｄｉｍｅｎｓｉｏｎｏｆ3×3×8ｍｍ3.ＴｈｅｏｓｃｉｌｌａｔｉｎｇｌａｓｅｒｔｒａｖｅｌｓｔｈｒｏｕｇｈｏｎｅｓａｍｐｌｅａｌｏｎｇＸａｘｉｓａｎｄｔｈｅｏｔｈｅｒａｌｏｎｇＹａｘｉｓ〔ｔｈｅａｎｇｌｅｓｂｅｔｗｅｅｎｔｈｅｃｒｙｓｔａｌｌｏｐｈｙｓｉｃａｘｉｓａｎｄｔｈｅ…