Dynamic heterogeneity in the self-induced spin glass state of elemental neodymium.

Spin glasses are magnetic materials exhibiting numerous magnetization patterns, that randomly vary both in real space and in time. To date, it is still not well understood what the nature of these spatiotemporal dynamics is, namely if they are completely random or if there are relevant and correlated length and time scales. Here, we demonstrate dynamic heterogeneity in the aging dynamics of elemental neodymium. We used spin-polarized scanning tunneling microscopy in combination with atomistic spin dynamics simulations to image the locally ordered magnetic patterns in the self-induced spin glass state and tracked the induced spatiotemporal dynamics in response to external perturbations. We observed that the real-space magnetization exhibited a coexistence of slow and fast dynamics coinciding with particular length scales. We adapted a wavelet paradigm to identify and correlate local spatial order with its dynamical evolution. These results provide a platform to study dynamics in spin glasses beyond the mean-field limit, linking to a generalized picture of glasses.