We provide experimental and numerical evidence for thermal excitations within and among magnetic mesospins, forming artificial spin ice structures. At low temperatures, a decrease in magnetization and increase in susceptibility is observed with increasing temperature, interpreted as an onset of thermal fluctuations of the magnetic texture within the mesospins. At elevated temperatures a pronounced susceptibility peak is observed, related to thermally induced flipping of the mesospins and a collapse of the remanent state. The fluctuations, while occurring at distinct length- and energy-scales, are shown to be tunable by the interaction strength of the mesospins.
@article{arxiv.2205.00938,
title = {Thermal excitations within and among mesospins in artificial spin ice},
author = {Björn Erik Skovdal and Samuel D. Slöetjes and Merlin Pohlit and Henry Stopfel and Vassilios Kapaklis and Björgvin Hjörvarsson},
journal= {arXiv preprint arXiv:2205.00938},
year = {2023}
}