Visualizing Spin-Dependent Molecule Symmetry at an Organic-Ferromagnetic Spinterface

As promising building blocks in spintronics, organic molecules have shown a variety of advantages including long spin coherence time and length as well as superparamagnetism. In addition, contacting with ferromagnetic (FM) materials, molecules induce so-called “spinterfaces” at the organic-FM boundaries, at which new spin-polarized states appear and change the magnetic properties in these hybrid systems. While the spinterface may influence performance in spinctronic devices, it may also extend the possibility of organic spintronics. To conduct an investigation into spinterfaces, we visualized the spin-distribution within single pentacene (PEN, C
₂₂
H
₁₄
) on FM Co nanoislands on Cu(111) via spin-polarized scanning tunnelling microscopy (SP-STM) [1]. Near the Fermi level, the widely-used semiconducting PEN molecules show not only spin-polarization opposite to the Co substrate, but also spin-dependent symmetries. Combined with first-principles calculations, the experimental findings agree with the pz-d hybridization model, in which spin-dependent bonding types can result in different molecule symmetries. Our observations exhibit locally-reversed spin-polarization after molecule deposition, and reveal a concise way to predict molecular spin-distribution for π -conjugated molecules such as PEN in organic-FM hybrid structures.