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%.

/pdf/highly-efficient-non-rare-earth-red-emitting-phosphor-for-3wgxp231in.pdf

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.

The substitutional chemistry and magnetoresistive properties of SFMO (Sr2FeMoO6) have been extensively studied in recent years. We report two new analogue Ruddlesden−Popper phases of SFMO:  Sr3FeMoO7 and Sr4FeMoO8. Both phases have a tetragonal structure (I4/mmm) with no Fe/Mo cation order. Neutron diffraction data suggest that there is no long-range spin order in Sr3FeMoO7, whereas antiferromagnetic order is evidenced for Sr4FeMoO8. Both materials show ferromagnetic hysteresis loops at 5 K with saturated moments of 0.8 μB and 0.2 μB for Sr3FeMoO7 and Sr4FeMoO8, respectively. Resistivity measurements show these materials to be semiconducting with band gaps of 125 and 46 meV for Sr4FeMoO8 and Sr3FeMoO7, respectively. No magnetoresistance effect was observed for either of the materials.

Synthesis, Structure, and Properties of Two New Ruddlesden−Popper Phase Analogues of SFMO (Sr2FeMoO6)

Magnetic frustration in the high-pressure Mn2MnTeO6 (Mn3TeO6-II) double perovskite.

The crystal structure of layered, tetragonal VO(H 2 AsO 4 ) 2 (a=9.1305 (1) A, c=8.1318 (2) A) has been refined in space group I4/mcm from laboratory X-ray powder diffraction data by the Rietveld method, giving R wp =10.1% and R F =5.5%. Disorder of the vanadium atoms over two sites results from infinite .V=O...V=O. chains orienting in the ±c-directions at random, due to the flexibility of the arsenate groups that link neighboring chains

Order and disorder of vanadyl chains: crystal structures of vanadyl dihydrogen arsenate (VO(H2AsO4)2) and the lithium derivative Li4VO(AsO4)2

The oxonitridoaluminosilicates M1.95Eu0.05Si5-xAlx N8-xOx (M: Ca, Sr, Ba; 0 ≤ x ≤ 1) are synthesized from stoichiometric mixtures of Ba3N2, Sr3N2, Ca3N2, α-Si3N4, EuN, and Al2O3 (BN crucible, 0.5 MPa N2, 1600 °C, 2 h).

Cation-Size-Mismatch Tuning of Photoluminescence in Oxynitride Phosphors.

The magnetic properties of the isomorphous compounds MnXO4·D2O (X = P, As) have been investigated by magnetic-susceptibility and low-temperature time-of-flight neutron powder diffraction methods. These materials behave as Curie–Weiss paramagnets at high temperatures and order antiferromagnetically below Neel temperatures of 33 and 24 K for X = P and As, respectively. The 4 K magnetic structures of the two compounds have been determined from time-of-flight neutron powder diffraction and consist of antiferromagnetic Mn–O–Mn chains in the [101] direction with ordered magnetic moments of 3.52(5) and 3.54(5)µB, for X = P and As, parallel to [101]. The crystal structures have also been refined precisely from the same data, and the resulting bond distances and angles are used to rationalise the relative strengths of the interchain magnetic superexchange interactions.

J. Paul Attfield

Papers

Synthesis, Structure, and Properties of Two New Ruddlesden−Popper Phase Analogues of SFMO (Sr2FeMoO6)

Magnetic frustration in the high-pressure Mn2MnTeO6 (Mn3TeO6-II) double perovskite.

Order and disorder of vanadyl chains: crystal structures of vanadyl dihydrogen arsenate (VO(H2AsO4)2) and the lithium derivative Li4VO(AsO4)2

Cation-Size-Mismatch Tuning of Photoluminescence in Oxynitride Phosphors.

Magnetic structures of MnPO4·D2O and MnAsO4·D2O from time-of-flight neutron powder diffraction data