New mechanism of kinetic exchange interaction induced by strong magnetic anisotropy

TL;DR

This paper reveals a new kinetic exchange mechanism induced by strong magnetic anisotropy that can lead to unexpectedly strong ferromagnetic interactions in certain magnetic complexes, confirmed by DFT analysis.

Contribution

It introduces a novel s-d kinetic exchange mechanism in strongly anisotropic magnetic ions, expanding understanding of magnetic interactions.

Findings

Discovery of a new s-d kinetic exchange contribution.

In non-collinear systems, this mechanism can induce strong ferromagnetic coupling.

DFT analysis confirms the presence and significance of this mechanism in lanthanide complexes.

Abstract

It is well known that the kinetic exchange interaction between single-occupied magnetic orbitals (s-s) is always antiferromagnetic, while between single- and double-occupied orbitals (s-d) is always ferromagnetic and much weaker. Here we show that the exchange interaction between strongly anisotropic doublets of lanthanides, actinides and transition metal ions with unquenched orbital momentum contains a new s-d kinetic contribution equal in strength with the s-s one. In non-collinear magnetic systems, this s-d kinetic mechanism can cause an overall ferromagnetic exchange interaction which can become very strong for transition metal ions. These findings are fully confirmed by DFT based analysis of exchange interaction in several Ln$^{3+}$ complexes.