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

In this Nanotalk, Dr. Trevor Almeida from the University of Glasgow, shares his experience using the DENSsolutions Lightning system to study magnetostructural transitions.
00:43 Introducing Trevor Almeida
02:39 Presentation
03:24 Motivation
07:20 Preparation & Characterisation
11:32 FeRh phase transition
28:35 Gradient-doped FeRh films
38:12 Conclusions
Q&A
40:33 Data processing and analysis
41:57 Critical thin film thickness
44:18 Gallium domain wall pinning
46:33 Beam masking
47:46 Atomic resolution magnetic properties
Abstract:
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).