Low energy consumption spintronics and nonlinear optics in multiferroic heterostructures

The evidence of the electric field control on the antiferromagnetic ordering in multiferroic bismuth ferrite (BiFeO₃ - BFO)[1] increased interest in low energy consumption logic and memory devices. However, to exploit such functionality for devices it is essential to attain eterministic control of ferromagnetism at the single domain scale. In a recent demonstration of room temperature electric field induced magnetization reversal [2], a ferromagnet/multiferroic heterostructure has been designed based on the combination of magnetoelectric coupling in BFO and exchange coupling between magnetic materials [3]. Understanding the underlying BFO domain architecture is a key parameter towards robust and reliable magnetization rotations. The most recent evidences of electrical control of magnetism in this system will be presented. I will also show that second harmonic generation (SHG), can further improve the heterostructures investigation and detect the distribution of ferroelectric domains in BFO thin films, non-invasively and unimpeded by transport properties. We use epitaxial strain for engineering different types of BFO domain patterns that are characterized by SHG, showing a unique relation between the domain distribution and the film symmetry. We then manipulate the BFO film by voltage poling and demonstrate the sensitivity of the SHG process to this manipulation. The concept applied to BFO is transferable to other multiferroics compounds thus indicating the general feasibility of SHG as a characterization technique for heterostructures in which buried ferroelectricity plays a key role in the emergence of magnetoelectric coupling.

[1] T. Zhao et al., Nat. Mater. 5, 823 (2006)
[2] J. T Heron et al., Nature 516, 371 (2014)
[3] M. Trassin et al., Phys. Rev. B 87, 134426 (2013)