인공고관절의 세라믹 볼 헤드의 기계적 안정성 평가를 위한 3 차원 유한요소 해석

The response of the worldwide scientific community to the discovery in 2008 of superconductivity at T c = 26 K in the Fe-based compound LaFeAsO1−x F x has been very enthusiastic. In short order, ot...

The puzzle of high temperature superconductivity in layered iron pnictides and chalcogenides

Colossal magnetoresistance (CMR) phenomena are observed in the perovskite-type hole-doped manganites in which the double-exchange ferromagnetic metal phase and the charge–orbital ordered antiferromagnetic phase compete with each other. The quenched disorder arising from the inherent chemical randomness or the intentional impurity doping may cause major modifications in the electronic phase diagram as well as in the magnetoelectronic properties near the bicritical point that is formed by such a competition of the two phases. One is the phase separation phenomenon on various time-scales (from static to dynamic) and on various length-scales (from glass-like nano to grain-like micron). The other is the enhanced phase fluctuation with anomalous reduction in the transition temperatures of the competing phases (and hence in the bicritical-point temperature). The highly effective suppression of such a phase fluctuation by an external magnetic field is assigned here to the most essential ingredient of the CMR physics. Such profound and dramatic features as appearing in the bicritical region are extensively discussed in this paper with ample examples of the material systems specially designed for this purpose. The unconventional phase-controls over the competing phases in terms of magnetic/electric fields and photo-excitations are also exemplified.

https://iopscience.iop.org/article/10.1088/0034-4885/69/3/R06/pdf

Critical features of colossal magnetoresistive manganites

Manganese-activated fluoride phosphors for high-efficacy warm white light-emitting diodes have been limited by low photoluminescence quantum yields. Here, Zhu et al. use an efficient cation exchange reaction to synthesize manganese phosphors with photoluminescence quantum yields as high as 98%.

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Highly efficient non-rare-earth red emitting phosphor for warm white light-emitting diodes

The manipulation of magnetic properties by an electric field in magnetoelectric multiferroic materials has driven significant research activity, with the goal of realizing their transformative technological potential. Here, we review progress in the fundamental understanding and design of new multiferroic materials, advances in characterization and modelling tools to describe them, and the exploration of devices and applications. Focusing on the translation of the many scientific breakthroughs into technological innovations, we identify the key open questions in the field where targeted research activities could have maximum impact in transitioning scientific discoveries into real applications. Magnetoelectric multiferroics, where magnetic properties are manipulated by electric field and vice versa, could lead to improved electronic devices. Here, advances in materials, characterisation and modelling, and usage in applications are reviewed.

Advances in magnetoelectric multiferroics.

A proton exchange membrane fuel cell (PEMFC) gas sensor is a promising and novel gas sensing device. However, the poor sensitivity and strong cross sensitivity of commercial carbon-supported-platinum (Pt/C) remain obstacles to its utilization. Here, we demonstrate that the issue can be addressed using mesoporous titanium niobium nitrides (Ti0.75Nb0.25N) synthesized using a solid–solid phase separation process. Pt nanoparticles supported on ternary transition metal nitrides enable the strong metal support interaction (SMSI), which changes the surface electronic structure and catalytic activity of the electrode material. Compared with the Pt/C-sensor, the selectivity of the Pt/Ti0.75Nb0.25N-based sensor to formaldehyde (HCHO) is significantly higher, while the response to other gases is effectively inhibited. In mixed gas tests, HCHO sensing of the Pt/Ti0.75Nb0.25N-sensor is still not affected (within 3.5% of the standard deviation limit). Furthermore, the Pt/Ti0.75Nb0.25N-sensor exhibits a much higher sensitivity (0.208 μA per ppm) toward HCHO when compared to the Pt/C-sensor (0.058 μA per ppm). The Pt/Ti0.75Nb0.25N-sensor also exhibits extraordinary long-term stability due to its electrochemical stability and SMSI of the electrode material. This work hence points to the design and development of a new sensing electrode system, which offers a combination of high selectivity and sensitivity when used in fuel-cell gas sensors.

/pdf/mesoporous-titanium-niobium-nitrides-supported-pt-fikddf501v.pdf

Mesoporous titanium niobium nitrides supported Pt nanoparticles for highly selective and sensitive formaldehyde sensing

By combining hydrogen and sulfur within diamond-anvil cells we synthesize ${({\mathrm{H}}_{2}\mathrm{S})}_{2}{\mathrm{H}}_{2}$ at 5 GPa and 373 K. Through a series of Raman spectroscopy, infrared spectroscopy, and synchrotron x-ray diffraction experiments we have constrained the phase diagram of ${({\mathrm{H}}_{2}\mathrm{S})}_{2}{\mathrm{H}}_{2}$ within a wide $P\text{\ensuremath{-}}T$ range. On compression we observe the phase transition sequence of ${\text{I-II-II}}^{\ensuremath{'}}\text{-III}$, where ${\mathrm{II}}^{\ensuremath{'}}$ is a previously unreported phase; at room temperature this sequence spans from 5 to 47 GPa, while the application of low temperatures stabilizes this sequence to 127 GPa $(l80\phantom{\rule{0.16em}{0ex}}\mathrm{K})$. Above these pressures we propose that phase III of ${({\mathrm{H}}_{2}\mathrm{S})}_{2}{\mathrm{H}}_{2}$ transforms to a nonmolecular ${\mathrm{H}}_{3}\mathrm{S}$ network. Our Raman and infrared measurements indicate that the transition from ${({\mathrm{H}}_{2}\mathrm{S})}_{2}{\mathrm{H}}_{2}$ to ${\mathrm{H}}_{3}\mathrm{S}$ is reversible at room temperature. X-ray diffraction reveals that the symmetry of the underlying S lattice of ${({\mathrm{H}}_{2}\mathrm{S})}_{2}{\mathrm{H}}_{2}$ and ${\mathrm{H}}_{3}\mathrm{S}$ is retained along this compression path up to at least 135 GPa.

/pdf/properties-and-phase-diagram-of-h-2-s-2-h-2-50u1yaks0g.pdf

Properties and phase diagram of (H 2 S)2 H 2

/pdf/charge-transfer-and-a-magnetic-crossover-in-hexagonal-baru1-4jsys3v3uq.pdf

Charge transfer and a magnetic crossover in hexagonal BaRu1-xMnxO3 perovskites

Magnetic properties of layered borocarbides $R{\mathrm{B}}_{2}\mathrm{C}$ $(R=\mathrm{Dy},$ Ho, and Er) have been studied by the magnetization and specific heat measurements at 1.8--300 K under the field up to 5 T. ${\mathrm{ErB}}_{2}\mathrm{C}$ has a basic two-sublattice antiferromagnetic order below ${T}_{\mathrm{N}}=16.3\mathrm{K}.$ ${\mathrm{HoB}}_{2}\mathrm{C}$ and ${\mathrm{DyB}}_{2}\mathrm{C}$ show the three-dimensional magnetic order below ${T}_{\mathrm{C}}=7.0\mathrm{K}$ and 8.5 K, respectively. However, they have still large magnetic fluctuations below ${T}_{\mathrm{C}}.$ The magnetic ordering temperatures of $R{\mathrm{B}}_{2}\mathrm{C}$ $(R=\mathrm{Dy},$ Ho, and Er) do not follow the de Gennes relation, where the ordering temperatures of ${\mathrm{HoB}}_{2}\mathrm{C}$ and ${\mathrm{DyB}}_{2}\mathrm{C}$ are suppressed. The suppressions of ordering temperature and the unconventional fluctuating ground states of ${\mathrm{HoB}}_{2}\mathrm{C}$ and ${\mathrm{DyB}}_{2}\mathrm{C}$ originate from the spin frustration effects. The instability of the unconventional magnetic phase associated with the frustration is significant in this series; the fluctuating ground state results from the complex spin--spin interactions or spin--quadrupole interactions.

/pdf/magnetic-properties-ofdyb2c-hob2c-anderb2c-1n8cxw05zr.pdf

Magnetic properties ofDyB2C,HoB2C,andErB2C

Doped manganite perovskites AMnO3 exhibit a rich variety of electronic properties, resulting from the interplay of charge (Mn3+/Mn4+), spin (Mn magnetic moment) and orbital (Mn3+ Jahn–Teller distortion) degrees of freedom. Magnetisation measurements and ESR spectra have been used to study a series of eight AMnO3 perovskites, in which the A cation sites are occupied by a distribution of 70% trivalent lanthanide and 30% divalent Ca, Sr or Ba ions. These all have a mean A cation radius of 1.20 A but different values of the cation size variance σ2. A change from orbital disorder to order (cooperative Jahn–Teller distortions) was previously found in the insulating regime at σ2
				≈ 0.005 A2. This work has shown that co-existence of the orbitally ordered and disordered phases is found in σ2
				= 0.0016–0.0040 A2 samples, with a difference of 40 K between their Curie temperatures. This is ascribed to competition between orbital ordering and microstructural lattice strains. At larger σ2 > 0.005 A2, the orbital ordering strains are dominant and only this phase is observed. This intermediate temperature phase segregation is one of many strain-driven separation phenomena in manganites.

J. Paul Attfield

Papers

Mesoporous titanium niobium nitrides supported Pt nanoparticles for highly selective and sensitive formaldehyde sensing

Properties and phase diagram of (H 2 S)2 H 2

Charge transfer and a magnetic crossover in hexagonal BaRu1-xMnxO3 perovskites

Magnetic properties ofDyB2C,HoB2C,andErB2C

Phase separation in manganites induced by orbital–ordering strains