Prof Gerrit van der Laan receives REXS 2025 Career Distinction Award

Gerrit van der Laan, Senior Research Fellow at Diamond Light Source, has received the prestigious REXS 2025 Career Distinction Award. The prize was presented at the closing session of the recent International Conference on Resonant Elastic X-ray Scattering (REXS 2025) held at Almadraba in Girona, Spain, recognising his "lifelong contributions in the field of X-ray resonant scattering". This honour credits a scientific journey marked by pioneering innovation and transformative insights into the fundamental properties of magnetism and condensed matter, largely enabled by the power of resonant X-ray techniques. The award was conferred by Dr Nicolas Jaouen, Chair of the International Scientific Advisory Committee, celebrating a legacy that has profoundly shaped the interpretation and application of soft X-ray magnetic resonant scattering.

Gerrit's career began with foundational work on X-ray magnetic circular dichroism (XMCD), a technique that measures the difference in absorption of left and right circularly polarised light in magnetic materials. He established the crucial "sum rules" that link absorption and dichroic spectra to the orbital and spin moments of the magnetic valence electrons. This work provided the theoretical bedrock for interpreting resonant magnetic scattering experiments, fundamentally connecting the observed spectral features to the microscopic magnetic structure of a material.

Dr Nicolas Jaouen announces the REXS 2025 Career Distinction Award on behalf of the International Scientific Committee and local organising committee, recognising Prof Gerrit van der Laan for his lifelong contributions to Resonant Elastic X-Ray Scattering.

A pivotal moment in his career occurred around the turn of the century while working at the Synchrotron Radiation Source (SRS) at Daresbury Laboratory. At that time, Gerrit was among the first to recognise and exploit the immense potential of resonant magnetic scattering using soft X-rays. This energy range is particularly effective because it aligns with strong absorption resonances, leading to greatly enhanced and highly dichroic signals. Magnetic multilayers, essential for spintronics, offered the perfect length scale to observe magnetic Bragg peaks when tuned to the transition-metal L edges, providing element-specific magnetic contrast. Using the dedicated high-vacuum diffractometer "Diffy," he performed groundbreaking measurements with polarised soft X-rays to probe nanoscale magnetic domains. One of his earliest landmark studies provided evidence for chiral magnetic domain structures in ultrathin FePd films, a discovery that laid the groundwork for the later, more widespread investigation of complex chiral spin textures like helimagnets, skyrmions, and hopfions.

The coherence of the synchrotron X-ray beam further enabled novel developments in Gerrit’s research. These advancements included tracking local magnetic reversal processes in FePd nanostripes using soft X-ray magnetic speckles. He also pioneered X-ray holography for imaging purposes, applying it to the study of single-layer nano-contact spin-transfer oscillators, magnetic droplet solitons, and the time-resolved dynamics of magnetic vortices and domain walls. These sophisticated imaging techniques provided unprecedented real-space and real-time views of magnetic phenomena.

His research revealed that circular dichroism (CD) in REXS allows for the direct experimental determination of the topological winding number, a fundamental property of these structures. Additionally, he showed that CD-REXS can measure the helicity angle in chiral spin structures through the "dichroism extinction effect." The shallow probing depth of soft X-rays also proved crucial for investigating surface-related phenomena, enabling the observation of a change in skyrmion helicity from Néel-type at the surface to Bloch-type in the bulk of Cu₂OSeO₃ over hundreds of nanometres.

These advances showcased how REXS could move beyond simply identifying a skyrmion lattice to revealing its intricate details, such as helicity, chirality, and depth-dependent variations. His team's use of REXS provided the first direct experimental observation of twisted skyrmions on the surface of a bulk crystal, overcoming the limitations of real-space imaging methods like Lorentz transmission electron microscopy (LTEM). The development of time- and spatially-resolved REXS even allowed for the observation of skyrmion crystallites rotating under a temperature gradient, revealing how these complex magnetic textures translate, rotate, and fluctuate in response to external stimuli. His influence also extends to novel topological spin textures, with his team using resonant elastic scattering to characterise the chiral bobber.

His research has consistently pushed the boundaries of what is observable with resonant X-ray scattering, leading to discoveries such as the skyrmion side-face state in chiral magnets and the evolution of emergent monopoles into magnetic skyrmion strings. The recent focus on slow equilibrium relaxation in chiral magnets, mediated by topological defects, further underscores his commitment to exploring the nuanced and complex dynamics of these systems. His collaborations extend across the globe, with studies being conducted at facilities like the SEXTANTS beamline at SOLEIL in France and the MaReS reflectometer at ALBA in Spain. This comprehensive and influential body of work makes the REXS 2025 Career Distinction Award a fitting tribute to his lasting impact.