Abstract
Single molecule magnets and single spin centres can be individually addressed when coupled to contacts forming an electrical junction. 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 centre. 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 coupled to contacts. Here, we utilize a highly corrugated hexagonal boron nitride monolayer to mediate the coupling between a cobalt spin in CoHx (x=1,2) complexes and the metal contact. While hydrogen controls the total effective spin, the corrugation smoothly tunes the Kondo exchange interaction between the spin and the underlying metal. Using scanning tunnelling microscopy and spectroscopy together with numerical simulations, we quantitatively demonstrate how the Kondo exchange interaction mimics chemical tailoring and changes the magnetic anisotropy.
Highlights
Single molecule magnets and single spin centres can be individually addressed when coupled to contacts forming an electrical junction
Studies on single molecule magnets (SMMs) containing 3d or 4f spin centres have revealed that chemical changes to the ligands surrounding the spin affect the magnetic anisotropy[11,12,13]
Magnetic anisotropy is not guaranteed in SMMs or single spin centres on coupling to contacts[9,16]
Summary
Single molecule magnets and single spin centres can be individually addressed when coupled to contacts forming an electrical junction. The scattering of the spin with the electron bath results in an energy renormalization of the spin’s eigenstate energy levels, similar to the case of a damped harmonic oscillator[17] This leads to a net reduction of the magnetic anisotropy, pushing the system closer to a Kondo state. To complement our experimental observations, we model transport through the CoHx complexes using Hamiltonians that incorporate magnetic anisotropy as well as coupling to the environment This is accomplished by parameterizing the environment through use of a dimensionless coupling constant À Jr0, describing the strength of the Kondo exchange interaction, À J, between the localized spin and the electron density r0 of the substrate near the Fermi level
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