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Title: Origin of anomalous magnetic noise from monopoles in Dy2Ti2O7
Plain: Magnetization noise in spin ice, produced by moving monopoles, does not follow a simple random-walk picture. Its spectrum and slow relaxation point to constrained monopole motion, but a full quantitative account is lacking.
Precise: In Dy2Ti2O7 at $T$ of about 0.5 to 3 K the magnetization-noise spectrum follows $S(\omega) \sim \omega^{-b}$ with $b$ between 1 and 2, and relaxation is faster than Arrhenius would allow at high $T$ and slower at low $T$. Derive $b(T)$ and the relaxation time $\tau(T)$ from a microscopic dipolar model with monopole hopping, without free parameters beyond the fitted exchange set. An answer is a model reproducing $S(\omega, T)$ quantitatively.
Settled by: Simulations of the fitted dipolar model with realistic monopole hopping that reproduce measured SQUID noise spectra across temperature.
Kind: phenomenon
Answer type: mechanism
References: (empty)
Literature status: partially-resolved
Status note: Dusad et al. (Nature 2019) measured the anomalous noise; Hallen et al. (Science 2022) attributed it to monopole motion on an emergent fractal of accessible sites.
Posed since: 2019