Scientific Highlights

The ability to start-up in extreme environmental conditions, including sub-freezing temperatures, is essential to the deployment of the fuel cell technology. Water produced in fuel cells at these temperatures can be in the super-cooled state, and freezing can lead to a rapid shutdown, as water cannot be removed anymore as a liquid. By segmenting a fuel cell, it is possible to prevent the propagation of freezing, which enables the cell operation even after the first freezing event occurred.

From new neutron powder diffraction experiments on the chiral cubic (P213) magnet manganese germanide (MnGe), we analyze all of the possible crystal symmetry-allowed magnetic superstructures that are determined successfully from the data. The incommensurate propagation vectors k of the magnetic structure are found to be aligned with the [100] cubic axes, and correspond to a magnetic periodicity of about 30 Å at 1.8 K. Several maximal crystallographic symmetry magnetic structures are found to fit the data equally well and are presented. These include topologically nontrivial magnetic hedgehog and “skyrmion” structures in multi-k cubic or orthorhombic 3+3 and orthorhombic 3+2 dimensional magnetic superspace groups respectively, with either potentially responsible for topological Hall effect. The presence of orthorhombic distortions in the space group P212121 caused by the transition to the magnetically ordered state does not favor the cubic magnetic hedgehog structure, and leave both orthorhombic hedgehog and skyrmion models as equal candidates for the magnetic structures. We also report on a combined mechanochemical and solid-state chemical route to synthesize MnGe at ambient pressures and moderate temperatures, and compare with samples obtained by the traditional high pressure synthesis.

We present magnetization and neutron powder diffraction studies in the temperature range 2K to 300K for oxygen stoichiometric R_1/3Sr_2/3FeO (R = Pr and Nd). From full symmetry analysis, we proposed two magnetic models by a combined application of irreducible representations and magnetic space groups. Both models fit equally well the neutron powder diffraction data.

The increasing risk of extended electricity supply disruptions and severe electricity price fluctuations  strongly motivate an evaluation of electricity supply resilience. In this direction, this research proposes a multicriteria decision support framework to assess resilience at a country level, based on three major dimensions: Resist, Restabilize and Recover. In total, 35 European countries are ranked according to their performance on 17 indicators, through a synergy of MCDA methods, techniques and communication protocols. The assessment framework has been extended to incorporate the Choquet Integral method, in order to accommodate potentially interacting pairs of criteria and negate their arbitrary effects on the final evaluation results. The analysis incorporates country data from credible international databases, as well as the preference information of a European energy expert. The results are envisaged to support energy policymakers in Europe and provide guidelines and areas for improvement at a country level.

GdSb_0.46Te_1.48, a nonsymmorphic Dirac semimetal with Dirac nodes at the Fermi level, has a rich magnetic phase diagram with one of the phases predicted to be an antiferromagnetic skyrmion state. In the current work, we investigate GdSb_0.71Te_1.22 through bulk magnetization measurements, single-crystal, and powder synchrotron X-ray diffraction, as well as single-crystal hot-neutron diffraction. We resolve a weak orthorhombic distortion with respect to the tetragonal structure and charge density wave (CDW) satellites due to incommensurate modulations of the crystal structure. At 2 K the magnetic structure is modulated with two propagation vectors, k_I = (0.45 0 0.45) and k_II = (0.4 0 0), with all their arms visible. While k_I persists up to the transition to the paramagnetic state at T_N = 11.9 K, k_II disappears above an intermediate magnetic transition at T₁ = 5 K. Whereas magnetic field applied along the c-axis has only a weak effect on the intensity of antiferromagnetic reflections, it is effective in inducing an additional ferromagnetic component on Gd atoms. We refine possible magnetic structures of GdSb_0.71Te_1.22 and discuss the possibility of hosting magnetic textures with non-trivial 3D+ 2 topologies in the GdSb_1−xTe_1+x series.