Ferromagnetic topological insulators exhibit the quantum anomalous Hall effect, which is potentially useful for high‐precision metrology, edge channel spintronics, and topological qubits. The stable 2+ state of Mn enables intrinsic magnetic topological insulators. MnBi₂Te₄ is, however, antiferromagnetic with 25 K Néel temperature and is strongly n‐doped. In this work, p‐type MnSb₂Te₄, previously considered topologically trivial, is shown to be a ferromagnetic topological insulator for a few percent Mn excess. i) Ferromagnetic hysteresis with record Curie temperature of 45–50 K, ii) out‐of‐plane magnetic anisotropy, iii) a 2D Dirac cone with the Dirac point close to the Fermi level, iv) out‐of‐plane spin polarization as revealed by photoelectron spectroscopy, and v) a magnetically induced bandgap closing at the Curie temperature, demonstrated by scanning tunneling spectroscopy (STS), are shown. Moreover, a critical exponent of the magnetization β ≈ 1 is found, indicating the vicinity of a quantum critical point. Ab initio calculations reveal that Mn–Sb site exchange provides the ferromagnetic interlayer coupling and the slight excess of Mn nearly doubles the Curie temperature. Remaining deviations from the ferromagnetic order open the inverted bulk bandgap and render MnSb₂Te₄ a robust topological insulator and new benchmark for magnetic topological insulators.

For three types of colloidal magnetic nanocrystals, we demonstrate that postsynthetic cation exchange enables tuning of the nanocrystal’s magnetic properties and achieving characteristics not obtainable by conventional synthetic routes. While the cation exchange procedure, performed in solution phase approach, was restricted so far to chalcogenide based semiconductor nanocrystals, here ferrite-based nanocrystals were subjected to a Fe²⁺ to Co²⁺ cation exchange procedure. This allows tracing of the compositional modifications by systematic and detailed magnetic characterization. In homogeneous magnetite nanocrystals and in gold/magnetite core shell nanocrystals the cation exchange increases the coercivity field, the remanence magnetization, as well as the superparamagnetic blocking temperature. For core/shell nanoheterostructures a selective doping of either the shell or predominantly of the core with Co²⁺ is demonstrated. By applying the cation exchange to FeO/CoFe₂O₄ core/shell nanocrystals the Neél temperature of the core material is increased and exchange-bias effects are enhanced so that vertical shifts of the hysteresis loops are obtained which are superior to those in any other system.

For the past several years, the JET scientific programme (Pamela et al 2007 Fusion Eng. Des. 82 590) has been engaged in a multi-campaign effort, including experiments in D, H and T, leading up to 2020 and the first experiments with 50%/50% D–T mixtures since 1997 and the first ever D–T plasmas with the ITER mix of plasma-facing component materials. For this purpose, a concerted physics and technology programme was launched with a view to prepare the D–T campaign (DTE2). This paper addresses the key elements developed by the JET programme directly contributing to the D–T preparation. This intense preparation includes the review of the physics basis for the D–T operational scenarios, including the fusion power predictions through first principle and integrated modelling, and the impact of isotopes in the operation and physics of D–T plasmas (thermal and particle transport, high confinement mode (H-mode) access, Be and W erosion, fuel recovery, etc). This effort also requires improving several aspects of plasma operation for DTE2, such as real time control schemes, heat load control, disruption avoidance and a mitigation system (including the installation of a new shattered pellet injector), novel ion cyclotron resonance heating schemes (such as the three-ions scheme), new diagnostics (neutron camera and spectrometer, active Alfvèn eigenmode antennas, neutral gauges, radiation hard imaging systems…) and the calibration of the JET neutron diagnostics at 14 MeV for accurate fusion power measurement. The active preparation of JET for the 2020 D–T campaign provides an incomparable source of information and a basis for the future D–T operation of ITER, and it is also foreseen that a large number of key physics issues will be addressed in support of burning plasmas.

Electronic stopping has been investigated experimentally for slow ${\text{H}}^{+}$ and ${\text{He}}^{+}$ ions $\left(v<0.6\text{a}\text{.u}\text{.}\right)$ in polycrystalline Au and Cu, by means of time-of-flight low-energy ion scattering. Measurements were performed in backscattering geometry using polycrystalline films of several nanometers thickness; high-resolution Rutherford backscattering spectrometry was used for precise thickness calibration $\left(<4\%\right)$. Absolute stopping cross-section data for Cu and Au were obtained down to $v\sim 0.07\text{a}\text{.u}\text{.}$ Both Au and Cu exhibit a rather sharp, distinctive threshold velocity of $\sim 0.18\text{a}\text{.u}\text{.}$ for excitation of $d$ electrons by ${\text{H}}^{+}$ and ${\text{He}}^{+}$. Below this threshold, projectiles interact exclusively with $s$ electrons.