Fig. 3

Spontaneous evolution of the monopole density during a wait time in zero applied field. This is gauged by the growth of magnetisation (M) and monopole current density (J_m = dM/dt) after a field is applied; comparison of the different isotopic samples reveals the effect of nuclear spins on the monopole mobility. a ¹⁶²Dy₂Ti₂O₇ (¹⁶²Dy) and b ¹⁶³Dy₂Ti₂O₇ (¹⁶³Dy), both measured at T = 80 mK, and c Ho₂Ti₂O₇ (HTO, T = 200 mK). ^nat Dy₂Ti₂O₇ (DTO) can be seen in Supplementary Fig. 4. The samples were first prepared using the AQP protocol outlined in (d) and discussed further in Methods. After the specified wait periods, a field of 0.08 T was applied and the magnetisation as a function of time was recorded. All measurements shown in the figure were made with the field along the [111] axis; examples for other directions are given in the Supplementary Figs. 10 and 11. e Plot of the value of the magnetisation M obtained after the first 400 s for the three samples shown to the left, and for ^natDy₂Ti₂O₇ vs. log wait time. Note that the magnetisation values at 400 s remain far from the expected equilibrium value. f The monopole current J_m = dM/dt at t = 0 for the three samples shown to the left vs. log wait time. Also shown is the monopole current for ^natDy₂Ti₂O₇, and the monopole current for Ho₂Ti₂O₇ measured at 80 mK