Measuring Quantum and Functional Materials on I16

The I16 beamline has been used to characterise the order in a wealth of different functional materials, such as centrosymmetric skyrmion hosts, ferroelectric materials and multiferroics.

Bismuth ferrite, BiFeO_3, is a canonical example of a type-1 room temperature multiferroic and one of the most promising materials for realising the electrical switching of magnetic order in materials. In previous non-resonant x-ray diffraction experiments performed at I16 it was observed that bulk single crystals of BFO with a single ferroelastic domain display three antiferromagnetic cycloidal domains, with each domain being up to 500µm in size [1], each defined by the magnetic propagation vectors, k₁ = (δ, δ, 0)_h,  k₂ = (δ, -2δ, 0)_h and k₃ = (-2δ, δ, 0)_h.  By contrast, epitaxial thin film samples of (111)_pc BFO grown on SrTiO₃ (STO) comprise three structural domains that are monoclinic (space group Cc) and related by the three-fold symmetry that is present in the bulk. These domains are on the order of 100nm’s in size and, are coupled to the magnetism such that each antiferromagnetic cycloidal domain maps uniquely onto one monoclinic domain [2]. In subsequent experiments on BFO/STO we electrically switched the FE polarisation and investigated the effect on the magnetic structure, demonstrating that the magnetic moments rotate on average by 90°, and that the electric and magnetic order parameters are strongly coupled [3]. To remove the submicron domains present in the thin films, which is essential if these films are to be incorporated into device heterostructures, we used an orthorhombic perovskite substrate to break three-fold symmetry and thus reduce the (111)pc BFO film to a single monoclinic and therefore a single magnetic domain. BFO was grown on the orthorhombic substrate TbScO3 (TSO) and it was found that the film was largely composed of a single ferroelastic domain, which was also found to be a single magnetic domain, hence demonstrating that the orthorhombic substrate had indeed broken three-fold symmetry [4].

The I16 beamline is well suited to studying functional materials owing to its ability to reduce the beam size to study small pads on devices, as well as its ability to simultaneously study the structural, magnetic and domain characteristics of a sample, all of which are relevant to its potential in creating a device.

1. Johnson, R. D., Barone, P., Bombardi, A., Bean, R. J., Picozzi, S., Radaelli, P. G., ... & Chapon, L. C. (2013). Phys. Rev. Lett., 110(21), 217206.
2. Waterfield Price, N. W., Johnson, R. D., Saenrang, W., Maccherozzi, F., Dhesi, S. S., Bombardi, A., ... & Radaelli, P. G. (2016). Phys. Rev. Lett., 117(17), 177601.
3. Waterfield Price, N. W., Johnson, R. D., Saenrang, W., Bombardi, A., Chmiel, F. P., Eom, C. B., & Radaelli, P. G. (2017). Physical Review Applied, 8(1), 014033.
4. Waterfield Price, N. W., Vibhakar, A. M., Johnson, R. D., Schad, J., Saenrang, W., Bombardi, A., ... & Radaelli, P. G. (2019). Physical Review Applied, 11(2), 024035.