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

University Of Washington, Seattle WA

Investigators

Abstract

Non-Technical Abstract This project addresses the arrangement and properties of arrays of nanoscale magnets fabricated by lithography methods. The fundamental physics component will investigate, both by experiment and modeling, the stable magnetic configuration of such arrays subject to different perturbations introduced by different magnetic underlayers. It will also investigate the possibility of (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 to engineer 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 Abstract Single domain, nanoscale magnetic elements, fabricated by lithography, and patterned into ordered arrays, form excellent magnetic metamaterials with unusual properties. Typically, their behavior is dominated by macroscopic inter-element dipolar interactions, but here in addition, we propose microscopic exchange interactions to provide much needed additional freedom to engineer 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 materials physics and magnetic configuration of a spin-ice metamaterial, including its thermodynamic phase transitions, coupled through underlayers where the interactions between the nanoelements of the spin lattice are dominated by lateral exchange bias (EB). The EB, along different well-defined crystallographic directions, can also be added to the system at different stages of the spin-ice configurational evolution. (2) Alternatively, each element in the metamaterial can be a multilayer, with intra-element exchange interactions; the magnetic performance of such exchange exchange-coupled composite metamaterial, fabricated in large-area arrays by nanoimprint lithography, will be optimized for bitpatterned media. (3) Magnetic quantum cellular automata (MQCA) in specific nanomagnetic arrays to process information 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 perform elementary 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, using electrons, photons and scanning probes, will provide fundamental insight into the structure- property performance correlation, at appropriate length scales, of all these unique and tailored metamaterials. This proposal will also enable the PI to combine the simultaneous advancement of discovery with teaching, training, learning, and if appropriate, commercialization.