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

Susan Kempinger, Yu-Sheng Huang, Paul Lammert, Michael Vogel, Axel Hoffmann, Vincent H. Crespi, Peter Schiffer, and Nitin Samarth

Phys. Rev. Lett. 127, 117203 – Published 10 September 2021

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 the 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.

Received 3 April 2021
Revised 24 July 2021
Accepted 11 August 2021

DOI:https://doi.org/10.1103/PhysRevLett.127.117203

Physics Subject Headings (PhySH)

Magnetism Magneto-optical Kerr effect Spin ice

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Susan Kempinger ^1,2,*, Yu-Sheng Huang¹, Paul Lammert¹, Michael Vogel³, Axel Hoffmann⁴, Vincent H. Crespi¹, Peter Schiffer⁵, and Nitin Samarth ^1,†

¹Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802-6300, USA
²Department of Physics, North Central College, Naperville, Illinois 60540, USA
³Institute of Physics and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel, Heinrich-Platt-Straße 40, 34132 Kassel, Germany
⁴Materials Research Laboratory and Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
⁵Department of Applied Physics and Department of Physics, Yale University, New Haven, Connecticut 06520, USA