Electrodeposition of Magnonic V(tetracyanoethylene)₂ Thin Films

Molecule-based magnetic materials have been identified as promising candidates for application in magnonic technologies, owing not only to their solution processability but also because they can exhibit narrow ferromagnetic resonance (FMR) linewidths and low Gilbert damping coefficients─crucial prerequisites for the transmission of coherent magnons over macroscopic distances. In particular, V(TCNE)₂, a compound with a three-dimensional network structure composed of vanadium(II) centers linked by tetracyanoethylene (TCNE^•-) radical anions, displays magnonic properties comparable to yttrium iron garnet, the quintessential magnonic material in the field. However, existing solution and chemical vapor deposition methods for synthesizing V(TCNE)₂ require the use of highly reactive zero-valent molecular vanadium precursors, stymying research on this important material. Herein, we report a facile electrochemical method for the deposition of thin films of V(TCNE)₂ using readily obtainable and stable divalent vanadium precursors and TCNE^•- anions generated by electrochemical reduction. Magnetization measurements reveal that the films exhibit ferrimagnetic ordering above room temperature, consistent with V(TCNE)₂ films synthesized via other methods. Moreover, the electrodeposited films exhibit narrow FMR linewidths as low as 17.5 G and a low Gilbert damping coefficient of 1.1 × 10^-3, values that are on par with some currently integrated metallic magnonic materials. More generally, these results demonstrate that electrodeposition can provide a straightforward means of generating high-performance magnonic materials using readily available molecular precursors.