New Vertex Type to Study Phase Transition in Artificial Spin Ices

Artificial spin ices are frustrated magnetic nanostructures constructed based on single domain segments [1]. A new type of vertex with five segments is engineered to generate eight degenerate ground states. The vertex is like the square ice vertex but one the segments split into two parallel segments creating a magnetic quadrupole. The distance between the parallel segments (d) determines ground state configuration. Micromagnetic simulation, OOMMF has been used to sweep d, and the results show that eight configurations have the same energy at a specific distance, d₀ . A two-atom rectangular lattice has been made using this vertex. Stimulated annealing with Monte Carlo assitance along with magnetic field sweeping has been performed looking for phase transition behaviour of the lattice (Different antiferroquadrupolar and ferroquadrupolar ordering [2]).
[1] Wang, 1. RF, et al. "Artificial ‘spin ice’in a geometrically frustrated lattice of nanoscale ferromagnetic islands." Nature 439.7074 (2006): 303.
[2] Sklenar, Joseph, et al. "Field-induced phase coexistence in an artificial spin ice." Nature Physics 15.2 (2019): 191.