Scientific Highlights

Strontium ruthenate (Sr₂RuO₄) continues to present an important test of our understanding of unconventional superconductivity, because while its normal-state electronic structure is known with precision, its superconductivity remains unexplained. There is evidence that its order parameter is chiral, but reconciling this with recent observations of the spin part of the pairing requires an order parameter that is either finely tuned or implies a new form of pairing. Therefore, a definitive resolution of whether the superconductivity of Sr₂RuO₄ is chiral is important for the study of superconductivity.

The interplay between oxygen and spin ordering for the low oxygen doped Nd₂NiO_4.10 has been investigated by single-crystal neutron diffraction. We find a coexistence of the magnetic order below T_N  with the 3D ordering of excess oxygen atoms, which has not been previously observed for the homologous nickelates. Moreover, the magnetic ordering modulation vectors are no longer independent and exactly follow the modulation vectors of the oxygen ordering.

A better understanding of quantum spin liquids (QSLs), where spin dimer configurations are fluctuating even at the low- est temperatures, could be of use in quantum information, in superconducting or other technologies. This macroscopic collective state typically arises from geometrical frustration or low dimensionality. In the layered EDT-BCO, we report a QSL state, which is generated, on different bases, with the intrinsic disorder.

Quantum spin liquids are materials that feature quantum entangled spin correlations and avoid magnetic long-range order at T =0 K. Particularly interesting are two-dimensional honeycomb spin lattices where a plethora of exotic quantum spin liquids have been predicted. Here, we experimentally study an effective S = 1/2 Heisenberg honeycomb lattice with competing nearest and next-nearest-neighbour interactions.

Magnetic skyrmions are well-suited for encoding information because they are nano-sized, topologically stable, and only require ultra-low critical current densities j_c to depin from the underlying atomic lattice. Above j_c, skyrmions exhibit well-controlled motion, making them prime candidates for race-track memories. In thin films thermally-activated creep motion of isolated skyrmions was observed below j_c as predicted by theory.

Magnetic skyrmion is a topologically protected particle-like object in magnetic materials, appearing as a nanometric swirling spin texture. The size and shape of skyrmion particles can be flexibly controlled by external stimuli, which suggests unique features of their crystallization and lattice transformation process. Here, we investigated the detailed mechanism of structural transition of skyrmion lattice (SkL) in a prototype chiral cubic magnet Cu₂OSeO₃, by combining resonant soft X-ray scattering (RSXS) experiment and micromagnetic simulation...

Quantum materials have properties that defy conventional theories of solids. Explaining these unusual properties is a frontier in physics, which promises both technological applications and fundamentally new states of matter. Yb₂Ti₂O₇ is a center of attention in this work. While it becomes ferromagnetic at very low temperature, its excitation spectrum resembles that of a quantum spin liquid. We show using neutron scattering ...

Non-centrosymmetric superconductors (NCSCs) are promising candidates in the search for unconventional and topological superconductivity. The α-Mn-type rhenium-based alloys represent excellent examples of NCSCs, where spontaneous magneticfields, peculiar to time-reversal symmetry (TRS) breaking, have been shown to develop in the superconducting phase. By converse, TRS is preserved in many other isostructural NCSCs, thus leaving the key question about its origin fully open. Here, we consider ...

We report a comprehensive muon spectroscopy study of the Zn-barlowite series of S=1/2 kagomé antiferromagnets, Zn_xCu_4−x(OH)₆FBr, for x = 0.00 to 0.99(1). By combining muon spin relaxation and rotation measurements with state-of-the-art density-functional theory muon-site calculations, we observe the formation of both μ–F and μ–OH complexes in Zn-barlowite. From these stopping sites, implanted muon spins reveal the suppression of long-range magnetic order into a possible quantum spin liquid state upon the increasing concentration of Zn-substitution.

In the past years, the strategies used to break the Cu(In,Ga)Se₂ (CIGS) light to power conversion effi- ciency world record value were based on improvements of the absorber optoelectronic and crystalline properties, mainly using complex post-deposition treatments. To reach even higher efficiency values, fur- ther advances in the solar cell architecture are needed, in particular, with respect to the CIGS interfaces. In this study, we evaluate the structural, morphological and optoelectronic impact of an Al₂O₃ layer as a potential front passivation layer on the CIGS properties, as well as an Al₂O₃ tunneling layer between CIGS and CdS.

We demonstrate efficient transverse compression of a 12.5 MeV=c muon beam stopped in a helium gas target featuring a vertical density gradient and crossed electric and magnetic fields. The muon stop distribution extending vertically over 14 mm was reduced to a 0.25 mm size (rms) within 3.5 μs. The simulation including cross sections ...

3D magnetic nanostructures are of great interest due to the possibility to design novel properties and the benefits for both technological applications such as high-density data storage, as well as more fundamental studies.
One of the main challenges facing the realization of these three-dimensional systems is their fabrication, which includes the deposition of magnetic materials on 3D surfaces. In this work, the electroless deposition of Ni–Fe
on a 3D-printed, non-conductive microstructure is presented.

In the three-dimensional (3D) Heisenberg model, topological point defects known as spin hedgehogs behave as emergent magnetic monopoles, i.e., quantized sources and sinks of gauge fields that couple strongly to conduction electrons, and cause unconventional transport responses such as the gigantic Hall effect. We observe a dramatic change in the Hall effect upon the transformation of a spin hedgehog crystal in a chiral magnet MnGe through combined measurements of magnetotransport and small-angle neutron scattering (SANS).