Experimentelle Physik II


Image & Results Gallery (recent achievements)

Reversible switching between spiral and collinear magnetic order via oxidation and reduction

February 23, 2023

The every-day ferromagnets we use magnetically order due to the exchange interaction, i.e., the overlap of electronic wave functions of neighboring atoms.  It causes the spins to order parallel, and the superposition of their magnetic moments produces the magnetic field we hold characteristic for feroomagnets.  Another, more complicated coupling is caused by the so-called Dzyaloshinskii-Moriya interaction. It causes the emergence of a wide variety of interesting magnetic structures, such as spin spirals and skyrmions. In a recent study, we showed by spin-polarized scanning tunneling microscopy that the interchain coupling between manganese oxide chains on Ir(001) can reproducibly be switched from chiral to collinear antiferromagnetic by increasing the oxidation state of MnO2, while the reverse process can be induced by thermal reduction. The underlying structure–property relationship has been revealed by low-energy electron diffraction intensity analysis performed by collaborators at FAU Erlangen-Nürnberg. Density functional theory calculations suggest that the magnetic transition may be caused by a significant increase of the Heisenberg exchange which overrides the Dzyaloshinskii-Moriya interaction upon oxidation.  The results have been published in Phys. Rev. B 107, L060409 (2023).