Avalanches from the ground state in artificial square ice*

Avalanches are phenomena in which there is a cascade-like transition between two states, and are present in many material systems. Generally, avalanches are pinned at defects. These defects, however, are difficult to control, and thus the study of the avalanche process is rather difficult. In this work, we utilize the customizable nature of artificial spin ice to examine avalanche processes under well-controlled circumstances. Starting with the magnetic ground state of artificial square ice, magnetic force microscopy was performed at remanence after the islands were exposed to increasing magnetic fields. The results are used to study the avalanche processes, and effects of finite system size, as well as the relevant scaling of the avalanche process.