The Formation of Complex Spin Textures in La0.7Sr0.3MnO3 Artificial Spin Ice Arrays

Abstract

Artificial spin ices (ASIs) are lithographically patterned arrays of single domain magnetic nanoislands where the dipolar interactions between these Ising-like macrospins have served as the basis for investigating phenomena such as geometric frustration and emergent magnetic monopoles [1]. While the majority of ASI studies have utilized nanoislands composed of soft magnetic metals (e.g. permalloy), the use of complex oxides, such as La0.7Sr0.3MnO3 (LSMO), could permit room temperature studies of thermally-active ASIs (TC ~ 360 K) and serve as a platform for coupling the rich physics of both complex oxide heterostructures and ASI structures. In this work, we utilize x-ray photoemission electron microscopy (X-PEEM) to image LSMO-based brickwork ASI structures where a breakdown of the Ising model of individual nanoislands occurs at a critical coupling strength which balances intra- and inter-island magnetic interactions. For ASI structures with nanoislands of identical dimensions, the ASI lattice parameter controls the inter-island coupling strength, resulting in systems composed solely of single-domain magnetic nanoislands, or a mixture of single-domain and complex spin textures (CST, i.e. single and double vortex states). Analysis of magnetic ordering in X-PEEM images reveals that nucleation of CST in frustrated nanoislands is accompanied by a disruption in long-range ordering. While it is generally assumed that inter-island interactions in ASI systems only influence the ordering of the nanomagnetic ensemble, in this LSMO-based ASI system inter-island coupling can dictate both the spin texture within individual nanoislands and long-range magnetic ordering. These results suggest the potential to create tunable nanoisland domain states, providing a new direction in developing ASI systems with exotic phase transitions as well as novel nanomagnetic logic architectures.