Spin Relaxation in Single-Ion Magnets under the Slowing Down Effect Produced by the Stray Field of Ferromagnetic Microparticles

The quantum tunneling of magnetization accelerates magnetic relaxation in transition and rare-earth ion complexes and often leads to the degradation of the characteristics of single-molecule or single-ion magnets. On the other hand, the applied dc magnetic field slows down the quantum tunneling of magnetization and favors other channels of spin relaxation. In this work, the stray magnetic field related to ferromagnetic microparticles occurring in the SIM composite with PrDyFeCoB microparticles is proposed instead of the applied field. The adjustable remanent magnetization of microparticles makes it possible to control the required stray field, which can be used to tune the spin relaxation rate in the complexes surrounding the microparticles. In this case, a slow spin relaxation is observed at zero applied field.