Scientific Highlights

In our recent paper we examined YNiO₃ and proved that the RNiO₃ type material known for its metal-insulator transition is in fact a type II multiferroic. We provide direct evidence of an electric-field-driven switch of the noncolliear magnetic state finally confirming the proposed type II multiferroic nature of YNiO₃.

PSI Researcher used inelastic neutron scattering to show how collective lattice vibrations can be controlled by electric fields. These results indicate that different eigenmodes can couple in field in this incipient ferroelectric.

Molecular single-ion magnets act as ultra-small magnets that can retain their magnetization. When organized on a well defined surface, they could allow storing information at 100 and more times higher storage densities than nowadays available. 

In the present study performed at the Swiss Light Source an international research team investigated monolayers of two very similar types of organometallic single-ion magnets, that, however, behave very differently on a flat silver surface. They link the vastly different magnetic behavior with the different orientation and adsorption configurations on the surface.

Strontium titanate is a wide band gap semiconductor. Its surface can be rendered conductive by a mild annealing in vacuum. The present study reveals that by deposition of less than a monolayer of non-volatile organic molecules such as tetracyanoquinodimethane (TCNQ) this conductivity can be completely turned off. In view of the small size of TCNQ (ca. 1 nm) this could allow new pathways toward oxide-based electronics.

X-rays reveal a non-collinear magnetic state as the base for all-optical magnetization switching.

3d transition metals often exhibit a quenched orbital moment when in a solid state system. Therefore, the proposition of a large unquenched orbital moment for V in VI₃ caused some surprise and discussion in the scientific community. Experimental and theoretical works diverge on the fact of whether the orbital moment is quenched or not. In our work we have been able to give an answer this open issue, proposing also a model for the ground state of VI₃.

Rare ferrimagnet states in a phase competing antiferromagnet.

A novel approach to controlling the speed of magnetic processes has been found through resonant magnetic scattering in an antiferromagnetic Lanthanide intermetallics.

In an interdisciplinary project, researchers from the Laboratory of Nanoscale Biology in BIO  and the Laboratory for Condensed Matter in PSD have revealed the reaction between the nitrogen atoms of the amyloid-beta peptide and copper/zinc ions by using soft X-ray absorption spectroscopy.

Lithium fluoride is an important material which is technologically exploited in spintronics and organic light emitting devices. It turns out that there is a vast difference between the morphologies of ultrathin lithium fluoride grown on the (100) facet of a silver single crystal.  At room temperature dendrites are obtained while at elevated temperature lithium fluoride forms square islands. The system is an interesting model to study the crossover between diffusion limited aggregates and island growth.

A team of the Leibniz Institute for Solid State Research (IFW) from Dresden, Germany, led by Dr Alexey Popov has now demonstrated a record blocking temperature of 28 Kelvin at which the magnetic bistability still survives in a submonolayer of a chemically functionalized species of endofullerenes. In this research, X-ray magnetic circular dichroism measurements at low temperatures and high magnetic field at the X-Treme beam line are crucial. The results pave the way toward using such single-molecule magnets as information carriers or magnetic bits.

This experiment performed at SwissFEL shows how fast we can localize electrons out of an electron gas into correlated, well localized states of a material. It is based on a combined ultrafast x-ray absorption and diffraction experiment on an intermetallic system.

Within this synergetic collaboration, PSI scientists have investigated the correlation between magnetic and electronic ordering in NdNiO3 by tuning its properties through proximity to a ferromagnetic manganite layer. The main outcome is that the stray magnetic field from the manganite layer causes a novel ferromagnetic-metallic (FM-M) phase in NNO. This work demonstrates the utilization of heterostructure engineering for creating novel quantum phases.

The authors demonstrate the stability of ferromagnetic order of one unit cell thick optimally doped manganite (La0.7Ba0.3MnO3, LBMO) epitaxially grown between two layers of SrRuO3 (SRO). LBMO shows ferromagnetism even above SRO Tc. Density Functional Theory calculations help understand the reasons behind this interesting result.

The authors find that an annealing process can create a highly ordered network of two-dimensional line defects at the buried interface between a relaxed film and its substrate. The low dimensional network spacing is directly related to the lattice mismatch and can correspondingly be tuned by the choice of substrate.

The authors find using resonant and non-resonant x-ray diffraction on an x-ray free electron laser that the structural distortion and the underlying electronic structure of the charge density wave in TiSe₂ show different energetics at ultrafast timescales. This indicates that the lattice distortion stabilizes the charge density wave.

The interaction of light and magnetism at the nanoscale is a topic of fundamental interest and with potential impact to future spintronics applications. in this work we address theoretically and experimentally the effect of femtosecond laser pulse excitation on the magnetic, structural, and chemical stability of individual magnetic cobalt nanoparticles including the role of the substrate or matrix. Eventually, we discuss possible pathways to achieve laser-induced magnetic switching in individual nanostructures.

This work has been highlighted as "Editors' Suggestion" in Physical Review B.

X-rays and neutrons has been used to investigate the correlation between structural and magnetic chirality in magnetic fields and its impact on the polarization in multiferroic langasites. A long wavelength modulation of the magnetic structure has been found, and it is shown that the chirality of the crystals structure connects to chirality of the magnetic structure that leads to an additional electric polarization in this field induced phase, which, depending on the christal chirality, can either increase the electric polarization or lead to a reversal of it for increasing magnetic fields. The theoretical description based on allowed Lifshitz invariants intriguingly contain all the essential ingredients for the realization of topologically stable antiferromagnetic skyrmions.

A research team centered at the X-Treme beam line at the Swiss Light Source has demonstrated that spin-phonon coupling plays a major role in enhancing the magnetic stability of so-called lanthanide phthalocyanine double decker single-molecule magnets. This understanding is important in order to employ such molecules in future spintronics applications.

Via femtosecond x-ray diffraction, we observe an ultrafast increase of the octahedral rotation angle in the perovskite EuTiO₃ after ultrafast laser excitation. This is opposite to what is expected from an increase in temperature. We ascribe this increase to an effective change of ionic sizes that transforms directly into a change of the Goldschmidt tolerance factor. Rotating oxygen octahedra at will opens up the possibility to control electronic and magnetic properties of perovskites on ultrafast timescales.

SIM beamline scientist Carlos Vaz was recognized as outstanding referee for providing high quality peer review for the Journal of Materials Chemistry C (Royal Society of Chemistry).

Direct manipulation of the atomic lattice using intense long-wavelength laser pulses has become a viable approach to create new states of matter in complex materials. Conventionally, a high-frequency vibrational mode is driven resonantly by a mid-infrared laser pulse and the lattice structure is modified through indirect coupling of this infrared-active phonon to other, lower-frequency lattice modulations.

In the week of April 1-5 PSI welcomes 20 PhD students and postdocs taking part in the European HERCULES 2019 school on Neutron and Synchrotron Radiation. They will attend lectures and perform two days of practical courses at several beam lines of the Swiss Light Source.