The origin of the large magnetoelectric coupling in the ceramic Ba 0.1 Bi 0.9 (Ti 0.9 Zr 0.1 ) 0.1 Fe 0.9 O 3

International audienceAbstract 57 Fe Mössbauer spectrometry and x-ray powder diffraction are conducted to examine the structure and the local magnetic order at the level of Fe sites of Ba 0.1 Bi 0.9 (Ti 0.9 Zr 0.1 ) 0.1 Fe 0.9 O 3 ceramic. The Mössbauer spectra in the temperature range of 77 K–623 K were analyzed using a discrete distribution of hyperfine field, indicating that the Néel temperature T N was about 603 K. The ceramic Ba 0.1 Bi 0.9 (Ti 0.9 Zr 0.1 ) 0.1 Fe 0.9 O 3 remains stable in the rhombohedral structure ( R 3 c ) in the temperature range of 300 K–800 K. The anomaly of volume below T N , as detected from the model Debye–Gruneissen, reveals the presence of magnetoelastic coupling in this compound. The total polarization ( P ) obtained from Rietveld refined atomic positions is found to depend on the magnetic order that leads to the decrease of the total polarization ( P ) through the anomaly volume. The reduction in the polarization by Δ P ∼ −2.4 μ C cm −2 suggests negative magnetoelectric interaction. The total polarization ( P ) obtained from Rietveld refined atomic is coupled with the magnetic ordering mediated by magnetoelastic coupling. The hyperfine field ( B hf ) dependence of polarization ( P ) at a temperature range below T N exhibits a linear evolution, confirming the linear magnetoelectric coupling. At room temperature, the linear magnetoelectric coefficient is about α ME ≈ 1.84 × 10 −9 s m −1

Fifteen research needs for understanding climate change impacts on ecosystems and society in the Norwegian High North

There is an urgent need to understand and address the risks associated with a warming climate for ecosystems and societies in the Arctic and sub-Arctic regions. There are major gaps in our understanding of the complex effects of climate change—including extreme events, cascading impacts across ecosystems, and the underlying socioecological dynamics and feedbacks—all of which need collaborative efforts to be resolved. Here, we present results where climate scientists, ecologists, social scientists, and practitioners were asked to identify the most urgent research needs for understanding climate change impacts and to identify the actions for reducing future risks in catchment areas in the Norwegian High North, a region that encompasses both Arctic and sub-Arctic climates in northern Norway. From a list of 77 questions, our panel of 19 scientists and practitioners identified 15 research needs that should be urgently addressed. We particularly urge researchers to investigate cross-ecosystem impacts and the socioecological feedbacks that could amplify or reduce risks for society.Peer reviewe