Phase-controlled hybrid magnonics enabled by synergistic interfacial spin-spin interactions

Nontechnical description: Hybrid material systems allow for harnessing physical interactions from crystal structures, magnetism, and material defects across the interfaces to achieve novel electronic and magnetic properties that are otherwise absent in each individual system. Exploiting magnetic interactions at the interface is a particularly attractive approach due to their high efficiency and tunability. By designing, synthesizing, and characterizing magnetic multilayers that integrate two dissimilar magnets and an interface, this project, via integrated computational and experimental efforts, aims to understand the complex interplay among the different types of fast (up to gigahertz) magnetic interactions that coexist at the interface. In fulfilling these goals, the research team will exploit state-of-the-art material engineering strategies including thin-film synthesis with precise control of composition and film thickness, and local electrical current injection. Upon completion, the project will develop new understanding towards harnessing cooperative physical interactions at interfaces for fast and reliable signal transmission and conversion, which plays a central role in the study of a wide variety of quantum materials and systems. The project will also increase participation of high-school students in STEM related careers. Technical description: The collective spin excitations (magnons) have received increased attention in novel constructions of hybrid systems exhibiting coherent phenomena. To date, investigation of hybrid magnonic systems has largely focused on using the non-propagating, ferromagnetic resonance modes. This scheme, however, leaves out the use of magnon wavevectors and their precessional phases as a potential state variable or control knobs. This project will design and create novel phase-controlled magnonic systems that operate on tailored, cavity magnon modes with finite wavelengths. By using magnetic heterostructures comprising a composite interlayer sandwiched by two dissimilar magnets, the team will explore tailored magnon-magnon coupling arising from synergistic interfacial spin-spin interactions. Such systems will exemplify a route towards the selective excitation, amplification, and on-demand phase control of short-wavelength (100 nm or less) magnon modes, and fill in a critical knowledge gap of coherent phenomena involving short-wavelength magnons. Technically, the project will explore competing magnon excitation channels from symmetric and antisymmetric spin coupling schemes, and deconvolute the magnon phase contributions from the intrinsic, wavevector-dependent characteristics and the extrinsic, angular momentum injections. This project will advance the fundamental understanding of competing spin-spin interactions from conventional static regime to a transformatively new dynamic regime. By synthesizing the novel magnon-magnon coupled cavity heterostructure, both the finite wavevector and magnon precession phase can be enabled as new state variables for signal transmission and transduction. The magnon-magnon coupling parameters along with the new theory and simulation capabilities will facilitate the understanding, prediction, and design of many other hybrid coherent/quantum systems involving magnons coupled to other solid-state quasiparticles. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.