Exchange-coupled magnetic metamaterials: fabrication, structure-property correlations, and applications

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Non-Technical AbstractThis project addresses the arrangement and properties of arrays of nanoscale magnets fabricatedby lithography methods. The fundamental physics component will investigate, both byexperiment and modeling, the stable magnetic configuration of such arrays subject to differentperturbations introduced by different magnetic underlayers. It will also investigate the possibilityof (a) using such arrays for next generation magnetic recording media for information storage, and(b) developing a magnetic approach for logic function in information processing. We will study interactions that can provide much needed additional freedom toengineer new properties, functionalities and applications. This proposal will also enable the PI to combine the simultaneous advancement of discovery with teaching, training, learning, and if appropriate, commercialization. Technical AbstractSingle domain, nanoscale magnetic elements, fabricated by lithography, and patterned intoordered arrays, form excellent magnetic metamaterials with unusual properties. Typically, theirbehavior is dominated by macroscopic inter-element dipolar interactions, but here in addition, wepropose microscopic exchange interactions to provide much needed additional freedom toengineer new properties, functionalities and applications in three distinct areas:(1) Geometrical frustration in a lattice of nanoscale ferromagnetic islands with dipolar interactions,leads to the formation of a spin-ice configuration; here we propose to investigate the materialsphysics and magnetic configuration of a spin-ice metamaterial, including its thermodynamic phasetransitions, coupled through underlayers where the interactions between the nanoelements of thespin lattice are dominated by lateral exchange bias (EB). The EB, along different well-definedcrystallographic directions, can also be added to the system at different stages of the spin-iceconfigurational evolution.(2) Alternatively, each element in the metamaterial can be a multilayer, with intra-elementexchange interactions; the magnetic performance of such exchange exchange-coupled compositemetamaterial, fabricated in large-area arrays by nanoimprint lithography, will be optimized for bitpatternedmedia.(3) Magnetic quantum cellular automata (MQCA) in specific nanomagnetic arrays to processinformation and perform Boolean logic operations is a promising alternative to CMOS technology.We will design and construct, for the first time, exchange-coupled logic gates that performelementary Boolean logic operations, based on a novel design of sub-50nm nanomagnet elements;two representive gates (AND and OR), will be demonstrated.Micromagnetic modeling and materials characterization, both routine and advanced, usingelectrons, photons and scanning probes, will provide fundamental insight into the structure- property performance correlation, at appropriate length scales, of all these unique and tailoredmetamaterials. This proposal will also enable the PI to combine the simultaneousadvancement of discovery with teaching, training, learning, and if appropriate, commercialization.