X-ray imaging of the magnetic configuration of a three-dimensional artificial spin ice building block

The extension of artificial spin systems to the third dimension offers advances in functionalities and opportunities for technological applications. One of the main challenges facing their realization is the fabrication of three-dimensional geometries with nanoscale resolution. In this work, we combine two-photon lithography with deformation-free pyrolysis and a GdCo coating to create a three-dimensional (3D) tripod structure that represents a building block of an 3D artificial spin ice, surrounded by a two-dimensional magnetic film. We map the three-dimensional magnetic configuration of the structure and its surroundings using soft x-ray magnetic laminography. In this way, we determine the magnetic configuration of the tripod nanostructure to be in the low-energy two-in-one-out spin ice state, observed at the 2D vertex of a kagome ice and predicted for three-dimensional vertices of magnetic buckyball structures. In contrast to isolated vertices, the degeneracy of this state can be lifted by the surrounding film, which also offers a route toward the controlled injection of emergent charges. This demonstration of the building block of a 3D spin system represents the first step toward the realization and understanding of more complex 3D artificial spin systems.