SAMURAI – Harnessing the Unique Samarium Ion in Samarium Trihalides

In the fascinating realm of condensed matter physics and materials science, manipulating the magnetic properties of materials is an attractive endeavor. An important concept is the magneto-crystalline anisotropy, a property that dictates how a material's magnetic properties are directionally dependent on its crystalline structure. Achieving control over this property can unlock new technological pathways, from data storage to quantum computing. This requires a deep understanding of the interplay between Coulomb interactions—the repulsive forces between electrons—and the magnetic basis states of the material. One candidate to design materials with low magneto-crystalline anisotropy is the rare-earth element samarium (Sm), particularly as samarium(III). Samarium stands out due to its simple yet intriguing set of magnetic basis states. It spans only three levels from the J=5/2 multiplet, occupied by five electrons. This results in highly symmetrical electric and magnetic densities, making samarium an attractive candidate for developing materials with low magneto-crystalline anisotropy. However, probing these exotic states is not easy. Neutron scattering, a powerful technique for studying the internal magnetic landscape of materials, faces challenges with samarium. Natural samarium absorbs neutrons, which complicates the experiments. This is where the SAMURAI project innovates: by growing high-quality single crystals using the 154Sm isotope, which absorbs far fewer neutrons, we can unveil these materials' intriguing magnetic ground states. The SAMURAI project aims to study complex magnetic ordering and bond-dependent magnetic behavior within samarium compounds. One important goal is to explore exotic states such as the Kitaev quantum spin liquid—a state characterized by highly entangled quantum spins, which is important for our understanding of quantum materials and computation.

Designing materials with defined magneto-crystalline anisotropy is very important in condensed matter physics and materials science. This requires a deep understanding of the interplay between Coulomb interactions—the repulsive forces between electrons—and the magnetic basis states of the material. To design materials with low magneto-crystalline anisotropy, samarium (Sm) emerges as an exceptional candidate for exploration among the rare-earth elements. Samarium(III) showcases one of the smallest sets of magnetic basis states, comprised of only three levels from the J=5/2 multiplet, occupied by five electrons. The Coulomb interactions between these electrons result in a highly spherically symmetric electric and magnetic configuration, an attribute that makes samarium(III) compounds particularly interesting. The SAMURAI project aims to search for complex magnetic ordering and bond-dependent magnetic behavior, such as the Kitaev quantum spin liquid enabled by low magneto-crystalline anisotropy. Inelastic neutron scattering is an exceptionally powerful tool to identify exotic states like the Kitaev quantum spin liquid, but the high neutron absorption of natural samarium makes neutron scattering challenging. The growth of high-quality single crystals with the 154Sm isotope will enable the project, which dramatically reduces the neutron absorption, allowing us to identify the magnetic ground states. Finally, SAMURAI will add a strong and broad activity within neutron science to strengthen the Norwegian science and user community. From the perspective of the coming European spallation source, ESS, it is crucial for Norway to build competence and ensure a user community. This will be ensured through the use of the national neutron infrastructure NcNeutron, which will serve as a foundation for future use of ESS.