Vanadium tetracyanoethylene: An organic-molecule-based, low-loss ferrimagnetic and semiconducting coordination compound

Organic-based materials comprised mainly of lightweight compounds (e.g. carbon and nitrogen) can provide a unique pathway towards low-cost, ecologically-friendly, and easily configurable alternatives to currently utilized inorganic materials. In terms of spintronic, magnonic, and quantum information applications, organic-based magnetic materials remain relatively unexplored despite the vast catalog of available materials that have been identified over decades. One such material, vanadium tetracyanoethylene (V[TCNE]x ∼ 2), however, has demonstrated superb low- loss magnetic resonance properties competitive with yttrium iron garnet (YIG) which is considered the gold standard low-loss magnonic material. In contrast to YIG, though, V[TCNE]x boasts unique properties, such as its benign deposition, patterning capabilities, and facile on-chip integration that outperform YIG. Despite these attractive properties, the electronic, structural, and spin thermal properties in V[TCNE]x have not been well understood until recently.

In this seminar, I present an overview of this remarkable material and specifically focus on recent advancements and explorations into the structural influences and spin-thermal phenomena in V[TCNE]x. First, I cover the structural and optoelectronic properties of V[TCNE]x, responsible for its long-range magnetic ordering. Next, I present studies on the elastic and magnetoelastic properties in V[TCNE]x by statically straining thin films and observing a shift in its ferromagnetic resonance frequency arising from a strain-dependent crystal-field anisotropy. Finally, I demonstrate the presence of spin-thermal interactions via the spin Seebeck effect in V[TCNE]x, where excellent agreement with theory predictions allows for the extraction of specific magnonic properties, including the magnon diffusion length. These properties provide unique insight and understanding into the fundamental mechanisms and workings of this remarkable magnetic material. Such insights and advancements contribute to previous demonstrations of V[TCNE]x applications for spintronic, magnonic, and quantum information systems, and provide further support for the exploration of other organic-molecule-based materials and coordination compounds for similar applications.