Magnetic monopole dynamics in spin-ice compounds

Thomas Stöter, Mathias Doerr, Sergey Granovsky, Martin Rotter, Sergey Zherlitsyn, Jochen Wosnitza

Frustrated magnetic materials are characterized by competing magnetic interactions either due to geometrical arrangement or different exchange interactions. Typical strongly frustrated systems are the pyrochlore-lattice materials A₂B₂O₇ (A= rare earth, B=transition metal). Prominent examples are the spin-ice materials Ho₂Ti₂O₇ and Dy₂Ti₂O₇, for which the magnetic moments can be well described by classical Ising spins. In general, spin-lattice effects play an important role in these magnetic compounds and make it possible to study the thermally activated spin excitations in detail. These dynamic effects are directly connected to the kinetics and density of magnetic “monopoles” (equivalence to those monopoles postulated by DIRAC). Our dilatometric measurements show the different character of the individual temperature- and field-dependent states. The lattice-relaxation processes follow a stretch-exponential law. Extremely long relaxation processes were observed in the kagome-ice state. In summary, the experimental results provide direct access to the density and kinetics of the monopoles via magnetoelastic investigations.

Original publication: Phys. Rev. B 101, 224416 (2020).