Kondo Effect in a Neutral and Stable All Organic Radical Single Molecule Break Junction

Abstract

Organic radicals are neutral, purely organic molecules exhibiting an intrinsic magnetic moment due to the presence of an unpaired electron in the molecule in its ground state. This property, added to the low spin-orbit coupling and weak hyperfine interactions, make neutral organic radicals good candidates for molecular spintronics insofar as the radical character is stable in solid state electronic devices. Here we show that the paramagnetism of the polychlorotriphenylmethyl radical molecule in the form of a Kondo anomaly is preserved in two- and three-terminal solid-state devices, regardless of mechanical and electrostatic changes. Indeed, our results demonstrate that the Kondo anomaly is robust under electrodes displacement and changes of the electrostatic environment, pointing to a localized orbital in the radical as the source of magnetism. Strong support to this picture is provided by density functional calculations and measurements of the corresponding nonradical species. These results pave the way toward the use of all-organic neutral radical molecules in spintronics devices and open the door to further investigations into Kondo physics.

Proximity-Induced Shiba States in a Molecular Junction

“…We find that the normal state characteristics (and Kondo effect) of the molecular junctions are consistent with previous reports of the same molecule in completely gold break junctions [46] (see Supplemental Material for details [47]. Furthermore, from the linear conductance in the Kondo regime we estimate an asymmetry in the couplings (Γ L , Γ R ) to the leads of Γ L =Γ R ≈ 5 × 10 −4 .…”

Theory of magnetoresistance of organic molecular tunnel junctions with nonmagnetic electrodes

“…In particular, the Kondo effect has been observed in low temperature (typically 10 K) experiments on single molecules under relatively large applied magnetic fields (typically several Tesla). 8,9 The effect is a consequence of spin correlation between the charge carriers in the contact and in the molecule. This interaction leads to a conductance characterized by a zero-bias resonance, which is sensitive to an applied magnetic field.…”

Complex magnetic orders in small cobalt–benzene molecules

“…A meticulous experimental determination of the magnetic anisotropy of the molecule would be even pos-sible, as done for instance in single molecule tunnel junctions based on organic molecules. 46,47 During the preparation of this manuscript S.T. Akin et al 22 reported XMCD measurements for Co 3 Bz + 3 cluster with null spin-magnetic moment.…”