Artificial spin ice (ASI) [1] systems are two-dimensional arrays of single-domain nanomagnetic islands that are designed to study collective behavior of interacting magnetic systems. These nanoislands usually have a stadium shape so that the magnetization orients along the longer axis, i.e., the moments are Ising-like. Most research on ASI systems focuses on different arrangements of nanoisland arrays [2], but, recently, some studies have focused on modifying the shapes of nanoislands [3,4]. Here, we introduce a new design of nanoislands, the Y-shape island, which has three equal-length arms joining at the center, with 120° separation. This island has six possible moment configurations in which the magnetization on each arm points either toward the center or away from it. We fabricated such nanoislands from permalloy, arranged in a hexagonal lattice geometry (Fig 1). Since permalloy has little magnetocrystalline anisotropy, the magnetization of the nanoislands can be well-controlled by utilizing shape anisotropy. We annealed such samples above the Curie temperature and examined the moment configurations using magnetic force microscopy after the samples cooled back to room temperature. We find strong correlations among the complex moment arrangements of these islands, suggesting the possibility of new types of moment ordering and new phenomenological ways of describing these novel magnetic objects associated with their unusual symmetry.<br/>Work at Yale University was funded by the US Department of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Division under Grant No. DE-SC0020162. Work at the University of Minnesota was supported by NSF through Grants No. DMR-1807124 and DMR-2103711.

![](https://assets.underline.io/uploads/markdown_image/1/image/2edd3e78dd111803b2e2fb7c7778f707.jpg)

Figure 1. (a) A scanning electron microscopy image of Y-shape nanoislands in hexagonal geometry. (b) A magnetic force microscopy image taken after annealing at 550 degree C. The white and black dots correspond to the poles of the island moments. (c) The corresponding moment schematic.

Artificial Spin Ice with Y-shaped Nanomagnets

**Session chairs:** Tom Thomson, University of Manchester and Hikaru Nomura, Yoshishige Suzuki Lab, Osaka University



EOF - Patterned Films

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Artificial Spin Ice with Y-shaped Nanomagnets

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