Emergence of Interfacial Magnetism in Strongly-Correlated Nickelate-Titanate Superlattices.

Strongly-correlated transition-metal oxides are widely known for their various exotic phenomena. This is exemplified by rare-earth nickelates such as LaNiO, which possess intimate interconnections between their electronic, spin, and lattice degrees of freedom. Their properties can be further enhanced by pairing them in hybrid heterostructures, which can lead to hidden phases and emergent phenomena.

Elastic moduli from crystalline micro-mechanical oscillators carved by focused ion beam.

The elastic moduli provide unique insights into the thermodynamics of quantum materials, particularly into the symmetries broken at their phase transition. Here, we present a workflow to carve crystalline resonators via focused ion beam milling from small and oddly shaped crystals unsuitable for traditional measurements of elasticity. The accuracy of this technique is first established in silicon.

Order-to-Disorder Transition and Hydrogen Bonding in the Jahn-Teller Active NHCrF Fluoroperovskite.

Large quantities of high-purity NHCrF have been synthesized using a wet-chemical method, and its structural chemistry and magnetic properties are investigated in detail for the first time. NHCrF is a tetragonal fluoroperovskite that displays an ordering of the ammonium (NH) groups at room temperature and C-type orbital ordering. The ammonium groups order and display distinct signs of hydrogen bonds to nearby fluoride anions by buckling the Cr-F-Cr angle away from 180°.

Cobalt-free layered perovskites RBaCuFeO (R = 4f lanthanide) as electrocatalysts for the oxygen evolution reaction.

Co-based perovskite oxides are intensively studied as promising catalysts for electrochemical water splitting in an alkaline environment. However, the increasing Co demand by the battery industry is pushing the search for Co-free alternatives. Here we report a systematic study of the Co-free layered perovskite famil RBaCuFeO (R = 4f lanthanide), where we uncover the existence of clear correlations between electrochemical properties and several physicochemical descriptors.

Proximity-Induced Novel Ferromagnetism Accompanied with Resolute Metallicity in NdNiO Heterostructure.

Employing X-ray magnetic circular dichroism (XMCD), angle-resolved photoemission spectroscopy (ARPES), and momentum-resolved density fluctuation (MRDF) theory, the magnetic and electronic properties of ultrathin NdNiO (NNO) film in proximity to ferromagnetic (FM) La Sr MnO (LSMO) layer are investigated. The experimental data shows the direct magnetic coupling between the nickelate film and the manganite layer which causes an unusual ferromagnetic (FM) phase in NNO. Moreover, it is shown the metal-insulator transition in the NNO layer, identified by an abrupt suppression of ARPES spectral weight near the Fermi level (E ), is absent.

Correlation between Oxygen Vacancies and Oxygen Evolution Reaction Activity for a Model Electrode: PrBaCo O.

The role of the perovskite lattice oxygen in the oxygen evolution reaction (OER) is systematically studied in the PrBaCo O family. The reduced number of physical/chemical variables combined with in-depth characterizations such as neutron dif-fraction, O K-edge X-ray absorption spectroscopy (XAS), electron energy loss spectroscopy (EELS), magnetization and scanning transmission electron microscopy (STEM) studies, helps investigating the complex correlation between OER activity and a single perovskite property, such as the oxygen content. Larger amount of oxygen vacancies appears to facilitate the OER, possibly contributing to the mechanism involving the oxidation of lattice oxygen, i.

Potential-Induced Spin Changes in Fe/N/C Electrocatalysts Assessed by In Situ X-ray Emission Spectroscopy.

The commercial success of the electrochemical energy conversion technologies required for the decarbonization of the energy sector requires the replacement of the noble metal-based electrocatalysts currently used in (co-)electrolyzers and fuel cells with inexpensive, platinum-group metal-free analogs. Among these, Fe/N/C-type catalysts display promising performances for the reduction of O or CO , but their insufficient activity and stability jeopardize their implementation in such devices. To circumvent these issues, a better understanding of the local geometric and electronic structure of their catalytic active sites under reaction conditions is needed.

Quantifying Diffusion through Interfaces of Lithium-Ion Battery Active Materials.

Detailed understanding of charge diffusion processes in a lithium-ion battery is crucial to enable its systematic improvement. Experimental investigation of diffusion at the interface between active particles and the electrolyte is challenging but warrants investigation as it can introduce resistances that, for example, limit the charge and discharge rates. Here, we show an approach to study diffusion at interfaces using muon spin spectroscopy.

Laue three dimensional neutron diffraction.

This article presents a measurement technique and data analysis tool to perform 3D grain distribution mapping and indexing of oligocrystalline samples using neutrons: Laue three-dimensional neutron diffraction (Laue3DND). The approach builds on forward modelling used for correlation and multiple fitting of the measured diffraction spots relative to individual grains. This enables not only to identify individual grains, but also their position and orientation in the sample.

Design of magnetic spirals in layered perovskites: Extending the stability range far beyond room temperature.

In insulating materials with ordered magnetic spiral phases, ferroelectricity can emerge owing to the breaking of inversion symmetry. This property is of both fundamental and practical interest, particularly with a view to exploiting it in low-power electronic devices. Advances toward technological applications have been hindered, however, by the relatively low ordering temperatures of most magnetic spiral phases, which rarely exceed 100 K.

Tuning magnetic spirals beyond room temperature with chemical disorder.

In the past years, magnetism-driven ferroelectricity and gigantic magnetoelectric effects have been reported for a number of frustrated magnets featuring ordered spiral magnetic phases. Such materials are of high-current interest due to their potential for spintronics and low-power magnetoelectric devices. However, their low-magnetic ordering temperatures (typically <100 K) greatly restrict their fields of application.

Pushing the limits of magnetic anisotropy in trigonal bipyramidal Ni(ii).

Monometallic complexes based on 3d transition metal ions in certain axial coordination environments can exhibit appreciably enhanced magnetic anisotropy, important for memory applications, due to stabilisation of an unquenched orbital moment. For high-spin trigonal bipyramidal Ni(ii), if competing structural distortions can be minimised, this may result in an axial anisotropy that is at least an order of magnitude stronger than found for orbitally non-degenerate octahedral complexes. Broadband, high-field EPR studies of [Ni(MDABCO)Cl]ClO () confirm an unprecedented axial magnetic anisotropy, which pushes the limits of the familiar spin-only description.