Ice-Rule Driven Vertex Frustration and Ergodicity Breaking in a Kagome-Pentagonal Artificial Spin Ice

Artificial spin ice provides a versatile platform to study how local ice-rule constraints lead to frustration, slow dynamics, and ergodicity breaking. Recent work on the Apamea and stretched-pentagonal lattices showed that even perfect local ice-rule obedience can paradoxically generate frustration, as mutually incompatible vertex constraints prevent the lattice from reaching a globally ordered state. Building on this framework, we study a newly engineered Kagome–Pentagonal lattice fabricated via e-beam lithography that interlaces Kagome, T-type, and two-island vertices with competing local rules. Samples composed of order of 10³ nanomagnets were thermally annealed between 405 K and 449 K and imaged by XMCD-PEEM. Vertex populations show that Type I (Kagome) and α (two-island) vertices dominate (~90%), while ~60% of Type B “unhappy” T-vertices remain frustrated, revealing incomplete relaxation due to the coupling between Kagome and T-type sublattices. Ergodicity analysis using the Thirumalai–Mountain metric yields small exponents (γ ≈ 0.01-0.12), indicating glassy, weakly ergodicity breaking dynamics. Cross- and auto-correlation analyses further uncover cooperative spin rearrangements and temperature-dependent vertex transitions driven by the interplay of frustrated and unfrustrated motifs.