Diamond Concise Annual Review 2021/22

20 21 D I A M O N D L I G H T S O U R C E A N N U A L R E V I E W 2 0 2 1 / 2 2 D I A M O N D L I G H T S O U R C E A N N U A L R E V I E W 2 0 2 1 / 2 2 MagneticMaterials Group T heMagnetic Materials Group develops and uses a range of polarised X-ray probes, including Resonant Inelastic X-ray Scattering (RIXS), Resonant Elastic X-ray scattering (REXS), X-ray Absorption Spectroscopy (XAS) and PhotoEmission Electron Microscopy (PEEM) on beamlines I06, I10, I16, and I21 to tackle a variety of challenges and opportunities in exploiting the changes inmagnetic properties of materials. Areas covered include topological states of matter, superconductivity, spintronics (the study of electron spinning and associated magnetism in solid state devices), two-dimensional systems, skyrmions (particles that may provide new forms of data storage) and multiferroics. Over the last year, our research community has used these probes to gain fundamental insights into newmaterials and how to tune materials to discover exotic new properties. Research from this group this year has included developing new methods of fast and energy efficient computing storage and discovering new superconductors that operate at closer to room temperature. Developing a new approach to computing memory So-called ‘racetrack non-volatile memory’, developed by IBM, is one of the most innovative information technology concepts to emerge in the past two decades. It works by creating tiny ‘disturbances’ in an otherwise uniform magnetic medium, which are stored and retrieved by moving them along a track when needed. The difficulty of stabilising the disturbances and propelling them at high speed has prevented this concept from reaching the market. Previous work at Diamond showed that the antiferromagnetic material α-Fe 2 O 3 supports a family of disturbances (known as textures) that are potentially very stable. The team, from institutions in Singapore, the UK and USA, is now investigating how to gain full control over the formation of these textures. Antiferromagnetic textures are difficult to visualise, and the team used the powerful imaging techniques on beamline I06 to map the antiferromagnetic textures in exquisite detail. Using X-ray Photo-Emission Electron Microscopy (X-PEEM), they acquired images of these textures over a field of view of a fewmicrons. This is potentially a ground-breaking application for fast and energy- efficient computing. Understanding the formation and control of such textures and their application in energy efficient computing represents a significant milestone in the field of information and communication technology. Jani H et al. DOI: 10.1038/s41586-021-03219-6 Sourcing the next generation of information storage A South Korean research group is also using Diamond facilities to look for the next generation of information carriers. Ideal candidates need to be stable against external disturbances such as temperature or field fluctuations, allow for low-power manipulation and easy readout, and have a small footprint that allows for high packing densities. Magnetic skyrmions are stable whirling topological configurations in magnetic materials that make them promising candidates for the next generation of computer storage devices. Crystalline magnetic skyrmions are among the most promising replacements for conventional ferromagnetic computer memory. The researchers looked for direct evidence of the existence of magnetic skyrmions in ultra-thin SrRuO 3 films by using temperature-dependent Resonant Elastic X-ray Scattering (REXS) on beamline I16. The team observed exciting Hall effect data which is the fingerprint of magnetic skyrmions. Their results showed a newmagnetic order with the same temperature dependence topological Hall effects, which they believe corresponds to skyrmion lattice structure. This new quasi quantum particle could soon be used for magnetic racetrack memory. Sohn B et al. DOI: 10.1103/PhysRevResearch.3.023232 Discovering new superconductors Scientists have been searching for materials that are superconducting at closer to room temperature since the 1986 discovery of cuprates (copper oxide materials that superconduct at high temperatures). The discovery of infinite- layer nickelate (nickel oxide) superconductors has drawn a lot of attention. An important research focus has been whether nickelate superconductors are strongly correlated electronic systems like cuprates. A team of researchers from the SLAC National Accelerator Laboratory, Stanford University and Diamond investigated the structure of magnetic excitations in the nickelate. They recently made the first measurements of magnetic excitations that spread through the new material. They collected data on beamline I21 using the Resonant Inelastic X-ray Scattering (RIXS) instrument. RIXS is presently the only instrument that can extract magnetic excitations in the momentum space from thin film samples. The high energy resolution and high photon flux available at I21 also played a vital role in the success of this experiment. Early results provide direct experimental evidence that support the possible exhibition of strong correlations in infinite- layer nickelates. This work reveals the microscopic electronic structures of the nickelate and will inform the future design and synthesis of new unconventional superconductors. Lu H et al. DOI: 10.1126/science.abd7726