Modifying Perpendicular Artificial Spin Ice

Artificial spin ice (ASI) is a highly customizable model system for studying frustration and interaction in magnetic systems. Perpendicular implementations of ASI are advantageous in that they have intrinsically isotropic interactions between neighboring elements and the magnetic states of elements in the array can be accessed using Kerr microscopy. This allows for complete microstate characterization in situ with an applied field. To expand the potential of perpendicular ASI, the system can be modified to allow additional control over the preferred state. There are two symmetry breaking modifications we will consider in this system. The first is using a soft magnetic Ni₈₀Fe₂₀ (Py) underlayer. Previous studies have shown that we can increase interaction strength and also tunably break the lateral symmetry in the array by fabricating perpendicular ASI systems on a Py layer. The second is modifying interactions in perpendicular ASI by connecting neighboring islands with thin necks. The thickness and orientation of the necks determines the adjusted interaction strength. Unlike the soft magnetic underlayer, modifications due to inter-island connections are set during the fabrication process and are not tunable in situ. We use micromagnetic characterizations to quantify the impact of combining these two modifications on the interaction strength, and present initial results of fabricated samples with these two modifications.

Work performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, was supported by the U.S. DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.