The use of in-situ TEM techniques and Lorentz microscopy to study magnetostructural transitions


Dr. Trevor Almeida


Materials and Condensed Matter Group,
School of Physics and Astronomy,
University of Glasgow, UK

Session 1

Date: Wednesday, August 5, 2020
Time: 9 AM Central European Summer Time (CEST) | 3 PM China Standard Time (CST)

Session 2

Date: Wednesday, August 5, 2020
Time: 8 PM Central European Summer Time (CEST)  | 2 PM Eastern Standard Time (EST)

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In order to improve the functional properties of magnetic materials used in modern devices, it is often necessary to investigate the underlying processes on the nano-scale. Combining in-situ TEM experiments with a range of Lorentz microscopy techniques allows for direct imaging of the magnetic behaviour of nanostructures whilst under the influence of external stimuli; e.g. gas atmospheres, biasing, temperature, etc. Here, the simultaneous use of in¬-situ biasing and heating is used to investigate the magnetostructural transition and current-induced domain wall (DW) motion in FeRh thin films.

Equiatomic iron-rhodium (FeRh) has attracted much interest due to its magnetostructural transition from its antiferromagnetic (AF) to ferromagnetic (FM) phase and is considered desirable for potential application in a new generation of novel nanomagnetic or spintronic devices. Several scanning TEM techniques are performed to visualise the localised chemical, structural and magnetic properties of a series of FeRh films. Cross-sectional and planar FeRh samples have been prepared from bulk substrates and transferred onto biasing / heating e-chips by focused ion beam methods [1] or HF-etching of the substrates. The quantitative evolution of the growth and co-existence of AF / FM phases in cross-sectional and planar FeRh films are observed directly during in-situ heating using differential phase contrast (DPC) imaging [2]. Further, this localized analysis provides fundamental insight into the mechanistic domain dynamics of the AF to FM transition [3]. In addition, DPC imaging provides direct visualisation of the systematic thermally-induced phase boundary motion within Ir / Pd gradient-doped FeRh cross-sectional thin films. Finally, combining DPC imaging with both heating and the application of electrical current pulses in situ within the TEM reveals the current-driven motion of magnetic DWs within planar FeRh thin films.

[1] T. P. Almeida et al. J. Phys. Conf. Ser. 903, 012022 (2017)
[2] T. P. Almeida et al. Sci. Rep. 7, 17835 (2017).
[3] T. P. Almeida et al. Phys. Rev. Mat. 4(3), 034410 (2020).