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<jats:p>A key issue in metallic uranium and its related actinide compounds is the character of the f electrons, whether it is localized or itinerant. Here we grew well ordered uranium films on a W(110) substrate. The surface topography was investigated by scanning tunneling microscopy. The Fermi surface and band structure of the grown films were studied by angle-resolved photoemission spectroscopy. Large spectral weight can be observed around the Fermi level, which mainly comes from the f states. Additionally, we provided direct evidence that the f bands hybridize with the conduction bands in the uranium ordered films, which is different from previously reported mechanism of the direct f–f interaction. We propose that the above two mechanisms both exist in this system by manifesting themselves in different momentum spaces. Our results give a comprehensive study of the ordered uranium films and may throw new light on the study of the 5f-electron character and physical properties of metallic uranium and other related actinide materials.</jats:p>

<jats:p>We report a theoretical work on the properties of modulational instability and bright type nonlinear localized modes in one-dimensional easy-axis weak ferromagnetic spin lattices involving next-nearest-neighbor couplings. With a linear stability analysis, we calculate the growth rates of the modulational instability, and plot the instability regions. When the strength of the next-nearest-neighbor coupling is large enough, two new asymmetric modulational instability regions appear near the boundary of the first Brillouin zone. Furthermore, analytical forms of the bright nonlinear localized modes are constructed by means of a quasi-discreteness approach. The influence of the next-nearest-neighbor coupling on the Brillouin zone center mode and boundary mode are discussed. In particular, we discover a reversal phenomenon of the propagation direction of the Brillouin zone boundary mode.</jats:p>

<jats:p>The thickness-dependent magnetic anisotropy of obliquely deposited Fe(001)/Pd thin films on Mg(001) is investigated by fitting the field-dependent resonant field curve using the Kittel equation. In this study, three Fe film samples with thicknesses of 50 monolayers (ML), 45 ML, and 32 ML deposited at 0°, 45°, and 55°, respectively, are used. The magnetic anisotropy constant obtained from ferromagnetic resonance (FMR) spectra exhibits a dominant fourfold magnetocrystalline anisotropy (MCA) at the normal deposition angle with larger Fe thickness. However, the in-plane uniaxial magnetic anisotropy (UMA) is induced by a higher oblique deposition angle and a smaller thickness. Its hard axis lies between the [100] and [010] directions. The FMR data-fitting analysis yields a precise measurement of smaller contributions to the magnetic anisotropy, such as in-plane UMA. Due to MCA, when the magnetic field is weaker than the saturated field, the magnetization direction does not always align with the external field. The squared frequency-dependent resonant field measurement gives an isotropic Landé <jats:italic>g</jats:italic>-factor of 2.07. Our results are consistent with previous experiments conducted on the magneto-optical Kerr effect (MOKE) and anisotropic magnetoresistance (AMR) systems. Thus, a vector network analyzer ferromagnetic resonance (VNA-FMR) test-method for finding UMA in obliquely deposited Fe(001)/Pd bilayer ferromagnetic thin films, and determining the magnetic anisotropy constants with respect to the film normal deposition, is proposed.</jats:p>

<jats:p>Nd content was varied in <jats:inline-formula> <jats:tex-math><?CDATA ${\mathrm{Nd}}_{13.2-x}{\mathrm{Fe}}_{80.8+x}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>Nd</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>13.2</mml:mn> <mml:mo>−</mml:mo> <mml:mi>x</mml:mi> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>Fe</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>80.8</mml:mn> <mml:mo>+</mml:mo> <mml:mi>x</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_7_077503_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> B<jats:sub>6</jats:sub> (<jats:italic>x</jats:italic> = 0, 0.5, 1, and 1.5) to optimize the magnetic properties of sintered Nd–Fe–B/Tb–Fe–B composite magnets, which were prepared by mixing 9 g of Nd–Fe–B with 1 g of Tb<jats:sub>17</jats:sub>Fe<jats:sub>75</jats:sub>B<jats:sub>8</jats:sub> powder. In conventional magnets, by reducing Nd content, the coercivity of 10.4 kOe in Nd<jats:sub>13.2</jats:sub>Fe<jats:sub>80.8</jats:sub>B<jats:sub>6</jats:sub> decreases to 7.2 kOe in Nd<jats:sub>12.2</jats:sub>Fe<jats:sub>81.8</jats:sub>B<jats:sub>6</jats:sub>; meanwhile, in Nd–Fe–B/Tb–Fe–B magnets the coercivity does not decrease when reducing Nd content. In the intergranular phase, the Tb content increases owing to the reducing Nd content of the Nd–Fe–B alloy in the sintered composite magnets. Therefore, the excess Tb in Tb<jats:sub>17</jats:sub>Fe<jats:sub>75</jats:sub>B<jats:sub>8</jats:sub> enters the intergranular phase, and more Tb atoms can substitute for Nd at the grain boundary of the Nd–Fe–B phase, leading to a more significant increase in coercivity. The remanence increases with reducing Nd content, and the energy product of 39.1 MGOe with a high coercivity of 21.0 kOe is obtained in Nd<jats:sub>12.2</jats:sub>Fe<jats:sub>81.8</jats:sub>B<jats:sub>6</jats:sub>/Tb<jats:sub>17</jats:sub>Fe<jats:sub>75</jats:sub>B<jats:sub>8</jats:sub> magnets. These investigations show that magnetic properties can be further improved by regulating the element distribution in sintered composite magnets.</jats:p>

<jats:p>The local detection of magnetic domains of isolated 10 nm Fe<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub> magnetic nanoparticles (MNPs) has been achieved by field-variable magnetic force microscopy (MFM) with high spatial resolution. The domain configuration of an individual MNP shows a typical dipolar response. The magnetization reversal of MNP domains is governed by a coherent rotation mechanism, which is consistent with the theoretical results given by micromagnetic calculations. Present results suggest that the field-variable MFM has great potential in providing nanoscale magnetic information on magnetic nanostructures, such as nanoparticles, nanodots, skyrmions, and vortices, with high spatial resolution. This is crucial for the development and application of magnetic nanostructures and devices.</jats:p>

<jats:p>Coercivity mechanism in permanent magnets has been debated for many years. In this paper, various models of the coercivity mechanism are classified and re-examined by the comparison and contrast. Coherent rotation and curling models can reveal the underlying reversal mechanism clearly based on isolated grains with elliptic shapes. By contrast, the numerical methods consider inter-grain interactions while simulating the evolution of the spins and hysteresis loops with complicated shapes. However, an exact simulation of magnetic reversal in permanent nanomagnets requires many meshes to mimic the thin domain wall well.</jats:p> <jats:p>Nucleation and pinning are the two main coercivity mechanisms in permanent magnets. The former signifies the beginning of the magnetic reversal, whilst the latter completes it. Recently, it is proposed that the large difference between the intrinsic magnetic properties of the nucleation centers and those of the main phase can result in a large pinning field (self-pinning), which has the attributes of both traditional nucleation and pinning. Such a pinning explains the experimental data of permanent magnets very well, including the enhancement of the coercivity by the grain boundary pinning.</jats:p>

<jats:p>Significant efforts have been put into the recycling of bulk Nd–Fe–B sintered magnet wastes around the world in the past decade because bulk Nd–Fe–B sintered magnet wastes are valuable secondary rare-earth resources. There are two major facts behind the efforts. First, the waste magnets contain total rare-earth content as high as more than 30 wt.%, which is higher than most natural rare-earth mines. Second, the waste magnets maintain the physical and chemical properties of the original magnets even with deterioration of the properties on surfaces due to corrosion and contamination. In this review, various techniques for recycling bulk Nd–Fe–B sintered magnet wastes, the overall properties of the recycled Nd–Fe–B sintered magnets, and the mass production of recycled magnets from the wastes are reviewed.</jats:p>

<jats:p>Since the 1980s, Nd–Fe–B with largest energy product (<jats:italic>BH</jats:italic>)<jats:sub>max</jats:sub> approaching the theoretical limit has become the landmark of permanent magnetic material. The application spectrum for Nd–Fe–B continues to expand over time both in the industrial and commercial sectors, which leads to growing research interests for solving the long-standing drawbacks of Nd–Fe–B, i.e., poor corrosion resistance, low coercivity, high Dy/Tb and low La/Ce/Y consumption. Concerning the above obstacles, we aim to present the novel grain boundary restructuring (GBR) approach, from GB design, processing, to structure evolution and property evaluation with a focus on the corrosion and coercivity mechanism of the restructured 2:14:1-typed magnets. Starting with an introduction to the fundamental of GBR, two representative examples, high-electrode-potential (Pr, Nd)<jats:sub>32.5</jats:sub>Fe<jats:sub>62.0</jats:sub>Cu<jats:sub>5.5</jats:sub> and low-melting-point Dy<jats:sub>71.5</jats:sub>Fe<jats:sub>28.5</jats:sub>, are given with detailed descriptions of the advantages of GBR to enhance the intrinsic anti-corrosion stability and to strengthen the coercivity at low Dy consumption. Microstructure–property correlations are established to understand the critical importance of regulating the restructured GB phase to maximize the all-round performance of the 2:14:1-typed permanent magnets. Aiming at sustainable and balanced development of rare earth (RE) industry, the proceeding section proposes new prototypes of La–Ce and Y–Ce co-substitutions with dual benefits of stabilizing the 2:14:1 tetragonal phase and strengthening the intrinsic hard magnetism. The findings of additional REFe<jats:sub>2</jats:sub> intergranular phase delight that the GBR approach also opens up a new horizon of research and application to develop high-performance La/Ce/Y-rich permanent magnets with deliberately tailored GB phase.</jats:p>

<jats:p>Ta<jats:sup>5+</jats:sup> doped <jats:italic>β</jats:italic>-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> single crystals were grown by using the optical floating zone method, and then annealed in the air and nitrogen gas at 1400 °C for 20 hours. The transmittance spectra, photoluminescence (PL), x-ray irradiation spectra, and PL decay profiles of the samples were measured at room temperature. The relevant results show that the optical transmittance of the samples annealed in the air or nitrogen gas was improved. By drawing the <jats:inline-formula> <jats:tex-math><?CDATA ${({ahv})}^{2}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:mi mathvariant="italic">ahv</mml:mi> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_7_077801_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>–<jats:italic>hv</jats:italic> graph, it can be seen that the band gap decreased after being annealed in the air, but increased in nitrogen gas. The PL spectra and x-ray irradiation spectra show that the luminescent intensity of the sample annealed in the air increased substantially, while decreased for the sample annealed in nitrogen. The PL decay time of the Ta:<jats:italic>β</jats:italic>-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> annealed in the air increased significantly compared with that of the Ta:<jats:italic>β</jats:italic>-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> sample without annealing, but the tendency after annealing in nitrogen gas was opposite.</jats:p>

<jats:p>The phenomenon of secondary electron emission is of considerable interest in areas such as particle accelerators and on-board radio frequency (RF) components. Total secondary electron yield (TSEY) is a parameter that is frequently used to describe the secondary electron emission capability of a material. It has been widely recognized that the TSEY vs. primary electron energy curve has a single-hump shape. However, the TSEY–energy curve with a double-hump shape was also observed experimentally—this anomaly still lacks explanation. In this work, we explain this anomaly with the help of a millimetre-scale (mm-scale) silver pillar array fabricated by three-dimensional (3D) printing technology. The TSEY–energy curve of this pillar array as well as its flat counterpart is obtained using sample current method. The measurement results show that for the considered primary electron energy (40–1500 eV), the pillar array can obviously suppress TSEY, and its TSEY–energy curve has an obvious double-hump shape. Through Monte Carlo simulations and electron beam spot size measurements, we successfully attribute the double-hump effect to the dependence of electron beam spot size on the primary electron energy. The observations of this work may be of help in determining the TSEY of roughened surface with characteristic surface structures comparable to electron beam spot size. It also experimentally confirms the TSEY suppression effect of pillar arrays.</jats:p>