Field-tunable interactions and frustration in underlayer-mediated artificial spin ice

TL;DR

This paper demonstrates that by adding a soft ferromagnetic underlayer beneath artificial spin ice, researchers can tune interactions and induce frustration, enabling control over magnetic correlations and effective geometries.

Contribution

The study introduces a method to control interactions in artificial spin ice using a ferromagnetic underlayer, enabling tunable frustration and directional correlations.

Findings

Interaction strength varies with array geometry.

Underlayer magnetization influences correlation patterns.

Frustration can be induced in unfrustrated geometries.

Abstract

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