via radio-frequency electromagnetic excitation*

In a variety of fluorine containing systems, the muon spin relaxation (μSR) signal from entangled fluorine-muon-fluorine (F–μ–F) spins has been observed and successfully modelled in terms of magnetic dipole-dipole interactions between the muon (spin) and two fluorine (nuclear) magnetic moments. In principle, it should be possible to manipulate the F–μ–F eigenstates and their populations through electromagnetic excitation. Here, we report μSR measurements of the F–μ–F states in single crystal LiY_0.95Ho_0.05F₄ excited in situ with a continuous radio-frequency electromagnetic field, tuned to the highest energy transition of the F–μ–F eigenstates. Clear differences in the μSR signal are observed on application of the excitation field. To model the experimental data, a magnetic dipole-dipole interaction Hamiltonian was constructed for a μF₂Li₂Ho cluster whose geometry was determined by calculations of the muon stopping site, to which we add a term representing the interaction of the cluster with the applied excitation field. This work opens new avenues for exploring the manipulation of quantum states within the unique μSR experimental environment.