Prof. Jonas Fransson
Department of Physics and Astronomy, Uppsala University, Sweden
Electrical control and detection of magnetic states in magnetic molecules

We investigate the far-from-equilibrium nature of magnetic anisotropy and exchange interactions between molecular magnets embedded in a tunnel junction. By mapping to an effective spin model, these magnetic interactions can be divided into three types: isotropic Heisenberg, anisotropic Ising, and anisotropic Dzyaloshinski-Moriya contributions, which are attributed to the background nonequilibrium electronic structures. We further demonstrate that both the magnetic self- and exchange interactions can be controlled either electrically by gating and tuning the voltage bias, or thermally by adjusting the temperature bias. We show that the Heisenberg and Ising interactions scale linearly, while the Dzyaloshinski-Moriya interaction scales quadratically, with the molecule-lead coupling strength. The interactions scale linearly with the effective spin polarizations of the leads and the molecular coherence. Our results pave a way for smart control of magnetic exchange interactions at atomic and molecular levels.

The control of the magnetic interactions lead to an effective control of the magnetic state in the junction and we show that a dimer system can be driven from a singlet to a triplet state configuration, by only applying a source-drain voltage. In turn, these magnetically very different states influence the electronic conductivity through the molecular dimer from high to low such that the system can be utilized for electronically controlled magnetic switching applications.



[1] J. Fransson, J. Ren, and J.-X. Zhu, Phys. Rev. Lett. 113, 257201 (2014).

[2] J. Bylin, thesis, Uppsala University (2015).

[3] T. Saygun, thesis, Uppsala University (2015).


1997 — M. Sc. Engineering Physics, Uppsala University, Sweden.

2002 — Ph. D. in Physics, Dept. Physics, Uppsala Univ., Sweden.

2003 — 2007, post doc at KTH, Stockholm, and Los Alamos Natl. Lab., NM, USA

2008 to present — associate professor, Dept. Physics and Astronomy, Uppsala Univ., Sweden.

Research have focused on nanoscale structures, non-equilibrium, spin-dependent phenomena, magnetization dynamics, and scattering effects on surfaces.

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