Martin Wood Complex, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU
Dr Tim Butcher, Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy
Prof Hariom Jani
Abstract
Microscopy images detailing the domain structure of ferroic materials are key for the development of technological applications. Imaging antiferromagnetic domains is challenging considering the lack of sensitivity to common magnetic microscopy methods. Multiferroicity with the presence of two distinct ferroic orders further complicates the analysis. Soft X-ray microscopy is a powerful tool for the characterisation of materials due to the ability to probe chemical, magnetic and ferroelectric properties. The microscopy technique of soft X-ray ptychography is a recent development at synchrotrons that can achieve sub-10 nm spatial resolution. Imaging ferroic order with ptychography relies on the collection of diffraction patterns from various positions of the sample under resonant conditions, which correspond to energies at the L-edge for transition metals and M-edge in the case of rare earths. The success of the approach will be presented for several ferroic materials in thin film and nanoparticle form. In the case of the room-temperature multiferroic bismuth ferrite (BiFeO3), soft X-ray ptychography is able to provide unprecedented insight into the multiferroic domain structure by resolving both the antiferromagnetic spin cycloid and ferroelectric domains in a single image [1]. Ptychographic imaging provides clear evidence of magnetoelectric coupling by separation of the antiferromagnetic and ferroelectric components even in the collinear case by employing X-rays at the Fe L-edge or O K-edge, respectively [2]. Furthermore, opportunities for ptychographic studies of dynamics in ferroic systems will be demonstrated for magnetic domain walls in permalloy [3].
[1] T. A. Butcher et al., Advanced Materials 36 (2024), https://doi.org/10.1002/adma.202311157
[2] T. A. Butcher et al., Physical Review Applied 23, L011002 (2025), https://doi.org/10.1103/PhysRevApplied.23.L011002
[3] T. A. Butcher et al., arXiv:2408.14172 [cond-mat.mtrl-sci] (2025), https://doi.org/10.48550/arXiv.2408.14172