Quantum Engineering of Spin and Anisotropy in Magnetic Molecular Junctions

TL;DR

This paper investigates how the structural environment of a magnetic molecule in a junction influences its spin properties, demonstrating control over magnetic anisotropy and exchange interactions via substrate corrugation.

Contribution

It introduces a method to tune magnetic interactions in molecular junctions using substrate corrugation and combines experimental and numerical techniques for analysis.

Findings

Corrugation smoothly tunes Kondo exchange interaction.

Magnetic anisotropy can be controlled by substrate structure.

Chemical and structural effects on spin can be mimicked and quantified.

Abstract

Single molecule magnets and single spin centers can be individually addressed when coupled to contacts forming an electrical junction. In order to control and engineer the magnetism of quantum devices, it is necessary to quantify how the structural and chemical environment of the junction affects the spin center. Metrics such as coordination number or symmetry provide a simple method to quantify the local environment, but neglect the many-body interactions of an impurity spin when coupled to contacts. Here, we utilize a highly corrugated hexagonal boron nitride (h-BN) monolayer to mediate the coupling between a cobalt spin in CoHx (x=1,2) complexes and the metal contact. While the hydrogen atoms control the total effective spin, the corrugation is found to smoothly tune the Kondo exchange interaction between the spin and the underlying metal. Using scanning tunneling microscopy and spectroscopy together with numerical simulations, we quantitatively demonstrate how the Kondo exchange interaction mimics chemical tailoring and changes the magnetic anisotropy.