Disorder-induced Room Temperature Ferromagnetism in Glassy Chromites

[[abstract]]We report an unusual robust ferromagnetic order above room temperature upon amorphization of perovskite [YCrO3] in pulsed laser deposited thin films. This is contrary to the usual expected formation of a spin glass magnetic state in the resulting disordered structure. To understand the underlying physics of this phenomenon, we combine advanced spectroscopic techniques and first-principles calculations. We find that the observed order-disorder transformation is accompanied by an insulator-metal transition arising from a wide distribution of Cr-O-Cr bond angles and the consequent metallization through free carriers. Similar results also found in YbCrO3-films suggest that the observed phenomenon is more general and should, in principle, apply to a wider range of oxide systems. The ability to tailor ferromagnetic order above room temperature in oxide materials opens up many possibilities for novel technological applications of this counter intuitive effect.[[journaltype]]國外[[incitationindex]]SCI[[booktype]]電子版[[countrycodes]]GB

International Consensus Statement on Rhinology and Allergy: Rhinosinusitis

Background: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR‐RS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICAR‐RS‐2021 as well as updates to the original 140 topics. This executive summary consolidates the evidence‐based findings of the document. Methods: ICAR‐RS presents over 180 topics in the forms of evidence‐based reviews with recommendations (EBRRs), evidence‐based reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary. Results: ICAR‐RS‐2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidence‐based management algorithm is provided. Conclusion: This ICAR‐RS‐2021 executive summary provides a compilation of the evidence‐based recommendations for medical and surgical treatment of the most common forms of RS

Enhanced Magnetoresistance in Nanocrystalline Magnetite

The magnetic and magnetotransport properties of nanoparticulate magnetite with different grainsizes are investigated using x-ray diffraction, microscopy, magnetometry, and magnetoresistancemeasurements. The magnetization varies significantly with grain size and is sensitive to preparation conditions. The reduction in saturation magnetization in coprecipitated particles is probably due to the surface spin disorder. Magnetoresistance of pressed powder compacts is significantly enhancedin material composed of small grain size magnetite particles prepared by coprecipitation. Usefulmagnetoresistance persists well above room temperature in sintered ceramic material

Mössbauer and vibrational DOS studies of diluted magnetic tin oxides and nano iron oxides

The magnetic properties and Mössbauer results for SnO2 doped with 57Fe are reviewed, and the values of isomer shift and quadrupole splitting are compared with the results obtained by ab initio calculations. It is concluded that the exchange interactions between oxygen defects and magnetic atoms are responsible for long range magnetic interactions of dilute Fe ions dispersed in SnO2. Fe atom precipitated clusters may be formed in highly Fe doped SnO2 samples by annealing at relatively high temperatures for several hours. The reduction of the particle size to nano-scale dimensions induces magnetization, which can be associated with oxygen defects. We have measured the nuclear inelastic scattering (NIS) spectra of Fe oxides, and 57Fe and (Co or Mn) doped SnO2 synthesized mainly by sol–gel methods and we have derived the vibration density of states (VDOS). The local phonons are sensitive to the presence of precipitated clusters.Fil: Nomura, K.. University of Tokyo. School of Engineering; JapónFil: Rykov, A. I.. Mössbauer Effect Data Centre; China. University of Tokyo. School of Engineering; JapónFil: Mudarra Navarro, Azucena Marisol. Universidad Nacional de La Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rodriguez Torres, Claudia Elena. Universidad Nacional de La Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Errico, Leonardo Antonio. Universidad Nacional de La Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Barrero, Carmen Raquel. Universidad de Antioquía; ColombiaFil: Yoda, Y.. Japan Synchrotron Radiation Research Institute; Japó

Electrostatically driven charge-ordering in Fe₂OBO₃

Charge-ordering is an important phenomenon in conducting metal oxides: it leads to metal-insulator transitions in manganite perovskites (which show `colossal' magnetoresistances), and the Verwey transition in magnetite (in which the material becomes insulating at low temperatures when the conduction electrons freeze into a regular array). Charge-ordered `stripes' are found in some manganites and copper oxide superconductors; in the latter case, dynamic fluctuations of the stripes have been proposed as a mechanism of high-temperature superconductivity. But an important unresolved issue is whether the charge ordering in oxides is driven by electrostatic repulsions between the charges (Wigner crystallization), or by the strains arising from electron-lattice interactions (such as Jahn-Teller distortions) involving different localized electronic states. Here we report measurements on iron oxoborate, Fe2OBO3, that support the electrostatic repulsion charge-ordering mechanism: the system adopts a charge-ordered state below 317 K, in which Fe2+ and Fe3+ ions are equally distributed over structurally distinct Fe sites. In contrast, the isostructural manganese oxoborate, Mn2OBO3, has been previously shown to undergo charge-ordering through Jahn-Teller distortions. We therefore conclude that both mechanisms occur within the same structural arrangement