Event Details

Speaker: Hariom Jani, Royal Society University Research Fellow, University of Oxford

Platforms hosting topological magnetic solitons, such as skyrmions, merons, bimerons and their antiparticles, are promising for the design of novel computing paradigms [1]. However, ferromagnetic systems are inhibited by susceptibility to stray fields, long-range dipole fields and slower dynamics. To alleviate these issues, there has been a surge of interest in antiferromagnetic (AFM) counterparts, predicted to be robust, scalable and faster by 100-1000 times. However, experimental progress in antiferromagnetic spintronics has been hampered by spin compensation, making it difficult to detect and design AFM solitons.

I will discuss how we overcame these limitations by leveraging advances in (i) quantum materials design and (ii) X-ray imaging to tailor and interrogate nanoscale antiferromagnetism, respectively. We designed an antiferromagnetic phase transition [2] that mimics the topological physics of the celebrated Kibble-Zurek mechanism [3], from cosmology. This has resulted in the discovery and reproducible control of a wide family of topological AFM solitons, including AFM half-skyrmions and bimerons, in the classic antiferromagnet hematite at room temperature [4,5]. In parallel, we integrated antiferromagnetic vector mapping with state-of-the-art X-ray imaging modalities, including X-ray photoemission microscopy [4], transmission microscopy6 and holography [7]. This allowed us to tailor AFM states under distinct in-situ stimuli, including temperature [4], strain [6] and magnetic fields [7]. These X-ray techniques naturally lend themselves to the investigation of triggered dynamical phenomena in the ultra-fast regime. Hence, our work enables the exploration of ultra-fast nanoscale AFM dynamics, which is crucial for building next-generation AFM spintronic technologies [1,8].

References:

1 C Back, V Cros et al. Journal of Physics D: Applied Physics 53, 363001 (2020).

2 H Jani, J Linghu et al. Nature Communications 12, 1668 (2021).

3 FP Chmiel, et al. Nature Materials 17, 581 (2018).

4 H Jani, J-C Lin, et al. Nature 590, 74 (2021).

5 A Tan,* H Jani,* et al. Nature Materials 23, 205 (2024).

6 H Jani,* J Harrison,* et al. Nature Materials 23, 619 (2024).

7 J Harrison, H Jani et al. Optics Express 32, 5885 (2024).

8 ZS Lim,* H Jani* et al. MRS Bulletin 46, 1053 (2021).

Team Acknowledgement: This talk is a culmination of pioneering X-ray advances made in the P.G. Radaelli group (Oxford), and samples developed in the Ariando group, T. Venkatesan group (Singapore), C.B. Eom group (Wisconsin-Madison) and M. Bibes group (Paris). Research team includes J.C. Lin, J. Harrison, C. Godfrey, J. Chen, S. Prakash, S. Hooda, G.J. Omar, J. Hu, M. Lal, J. Schad, F. Maccherozzi, S. Finizio, J. Raabe, T.A. Butcher, N. Jaouen, H. Popescu, F. Kronast, A. Tan, M. Hogen, C. Castelnovo, S. Valencia, L. Iglesias, L. Arche. Large Scale facilities: Diamond, PSI, Soleil, ALBA and BESSY.