Monopolar and dipolar relaxation in spin ice Ho<sub>2</sub>Ti<sub>2</sub>O<sub>7</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 34134975.
- Also identified by DOI 10.1126/sciadv.abg0908 and PMC identifier 8208707.
- Licence recorded as CC BY-NC.
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Abstract
Ferromagnetically interacting Ising spins on the pyrochlore lattice of corner-sharing tetrahedra form a highly degenerate manifold of low-energy states. A spin flip relative to this "spin-ice" manifold can fractionalize into two oppositely charged magnetic monopoles with effective Coulomb interactions. To understand this process, we have probed the low-temperature magnetic response of spin ice to time-varying magnetic fields through stroboscopic neutron scattering and SQUID magnetometry on a new class of ultrapure Ho<sub>2</sub>Ti<sub>2</sub>O<sub>7</sub> crystals. Covering almost 10 decades of time scales with atomic-scale spatial resolution, the experiments resolve apparent discrepancies between prior measurements on more disordered crystals and reveal a thermal crossover between distinct relaxation processes. Magnetic relaxation at low temperatures is associated with monopole motion through the spin-ice vacuum, while at elevated temperatures, relaxation occurs through reorientation of increasingly spin-like monopolar bound states. Spin fractionalization is thus directly manifest in the relaxation dynamics of spin ice.