Diamond Annual Review 2025-26

The research encompasses a variety of challenges and opportunities in condensed matter physics and materials science, ranging from topological states of matter, superconductivity, spintronics, two-dimensional systems, skyrmions and multiferroics. The MMG also runs the Materials Characterisation Laboratory (MCL). The Diamond-II flagship I17 beamline will be a unique facility for performing polarised X-ray imaging from quantum and functional materials. A new window into the brain: laser powered electron microscopy accelerates connectome mapping Connectome mapping is the study of how neurons connect to form the brain’s networks. Mapping the brain’s wiring is one of neuroscience’s biggest challenges. Current electron microscopy methods are powerful, but slow and costly at whole-brain scale. Mapping a cubic millimetre of brain tissue can take months or years. The advanced laser-PEEM facility, part of the I06 beamline, Diamond’s Magnetic Materials Group (MMG) concentrates on emergent phenomena in quantummaterials using the capabilities of beamlines I06, I10, I16 and I21. Magnetic Materials Group was used to image brain tissue at synaptic resolution, hundreds of times faster than conventional techniques. Using ultra-thin mouse brain sections stained with osmium and mounted on gold-coated silicon wafers, the researchers achieved 20-nanometre resolution, enough to resolve individual synapses. With ultraviolet laser illumination, they reached gigavoxel-per-second imaging speeds. The advanced laser-PEEM showed that these high imaging rates could be achieved without damaging delicate brain samples. This approach could enable faster, high-resolution brain mapping and may also benefit pathology, materials science and nanotechnology. DOI: 10.1073/pnas.2521349122 Magnetic conversations at gigahertz speed A study carried out on the I10 BLADE beamline focused on how one magnetic material can wirelessly control another at gigahertz speeds. A helimagnet has a spiral magnetic structure. When microwaves make this spiral vibrate, it creates magnetic waves. These waves produce a changing magnetic field that can pass through a thin platinum layer and make a nearby magnet move in step with it. Using a three-layer stack made from a helimagnet, platinum and a nickel-iron ferromagnet and time-resolved resonant elastic X-ray scattering, researchers tracked the spin motion in both magnetic layers with picosecond resolution. Measurements at copper and iron resonances allowed them to compare how each layer moved during an oscillation cycle. They found that the nickel-iron layer became phase-locked to selected helimagnon modes in the helimagnet. Choosing different modes changed the phase relationship, while preserving the handedness of the spiral magnetic structure. The work points towards low-power spin-wave communication, where information could be encoded in frequency, phase and chirality rather than electric charge. It could help develop compact magnetic devices that communicate across thin layers without direct wiring. DOI: 10.1038/s41567-025-03148-5 Chiral magnons leave a measurable X-ray fingerprint in altermagnets Research form the I21 beamline demonstrated how the chirality, or handedness, of magnons can be measured in an altermagnet. Magnons are quantised spin-wave excitations: collective oscillations of magnetic moments within an ordered magnetic material. In certain systems, these excitations can be chiral, meaning their spin motion has a preferred rotational sense, either right-handed or left-handed. The material studied was chromium antimonide, a metallic altermagnet that retains magnetic order at room temperature. Altermagnets are of interest because they combine features of ferromagnets and antiferromagnets, while also allowing spin-dependent electronic behaviour without producing a large external magnetic field. To probe the magnon chirality, researchers used RIXS and compared the response to right- and left-circularly polarised X-rays, observing circular dichroism at the magnon energy. The dichroic signal reversed with crystal momentum, crystal orientation and magnetic domain handedness. This shows that chiral magnons leave a measurable X-ray fingerprint, providing a powerful way to identify altermagnetic behaviour and study chiral spin dynamics, even when individual magnon branches cannot be resolved directly. DOI: 10.1103/PhysRevLett.132.176701 17 18 Annual review 2025/26 Magnetic Materials Group