Abstract:
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.
References:
[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).
Biography:
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.