Analysis of the Internal Magentic Field of UBe13 Through μSR
Jack Li
St George's School
Floor Location : S 020 D

Uranium beryllium-13 (UBe13) is a characteristic heavy fermion whose properties strongly depend on the material's internal magnetic structure. Different models have been proposed to explain these properties, but additional experimental data is required. This project aims to offer new insight so that a rigorous model of its magnetic structure can be built. UBe13 is studied through muon spin spectroscopy (μSR) - a process where positive muons are produced and embedded into a sample, where they localize at a particular site. The local magnetic field causes precession of the muon spin at the Larmor frequency, creating signals that can provide measurements of the internal magnetic field. Results are analyzed, revealing two primary Larmor frequencies, consistent with lattice sites between adjacent uranium atoms, either aligned with, or at a 90 degree angle from the axis of the external magnetic field. The Fourier power of the two peaks correspond roughly to the expected distribution in muon stopping sites, although other interactions might be at play. At temperatures higher than the mobility limit, thermal energy causes the muon to travel between muon sites, forming a single peak. At lower temperatures, such thermal energy was removed, and the oscillation between lattice locations decreased, forming two distinct peaks in the spectrum. The applied magnetic field was used to induce a net magnetization in the UBe13 sample, which allowed for sensitive inter lattice measurements.