Field-Tunable Interactions and Frustration in Underlayer-Mediated Artificial Spin Ice

Artificial spin ice systems have opened experimental windows into a range of model magnetic through the control interactions among nanomagnet moments. This has previously been enabled by altering size and geometry their placement. Here we demonstrate that in artificial can be further controlled including soft ferromagnetic underlayer below Such substrate also breaks symmetry array when magnetized, introducing directional component to correlations. Using spatially resolved magneto-optical Kerr effect microscopy image demagnetized ground states, show correlation states depends on direction magnetization. Further, relative interaction strength nearest next-nearest neighbors varies significantly with geometry. We exploit this feature induce frustration an inherently unfrustrated square lattice geometry, demonstrating new possibilities for effective geometries two dimensional nanomagnetic systems.