Long-range Magnetic Ordering in Artificial Kagome Spin Ice

Abstract

The extent of magnetic ordering in highly-frustrated thermally-active artificial kagome spin ice is limited by the lowest achievable blocking temperature, as the moments freeze in before ordering is achieved [1]. A more substantial degree of magnetic ordering can be achieved by lowering the blocking temperature of the individual nanomagnets or by increasing the critical transition temperature for the system. We pursue an original approach of introducing interfacial Dzyaloshinskii-Moriya interactions, which lowers the blocking temperature while keeping the transition temperature unchanged [2]. Using this approach, we demonstrate that a seven-ring kagome structure consisting of 30 nanomagnets can be thermally annealed into its ground state. Furthermore, the spin-ice correlations extracted from extended kagome lattices are found to exhibit the quantitative signatures of long-range charge-order, thereby giving experimental evidence for the theoretically predicted continuous transition to a charge-ordered state. We also find that slight modifications of the nanomagnets at a vertex in the artificial kagome ice lead to an increase in the critical temperatures, and allow us to control the energy landscape. Our results provide the foundations for the tuning of magnetic ordering in several different artificial spin systems.