MOTYČKOVÁ, L. Magnetické vlastnosti samouspořádaných nanomagnetů FeRh [online]. Brno: Vysoké učení technické v Brně. Fakulta strojního inženýrství. 2020.

Posudek vedoucího

Arregi Uribeetxebarria, Jon Ander

The diploma thesis of Lucie Motyčková deals with the fabrication and characterization of FeRh nanostructures and nanoparticles using solid-state self-assembly routes. The thesis comprises extensive experimental work such as sample growth, characterization via scanning probe microscopy, magnetometry, chemical etching, and magnetic separation of nano-objects from a liquid. Some findings are also supported via simple modeling. Importantly, she demonstrates that FeRh nanostructure arrays with controlled size and morphology can be successfully fabricated while preserving the phase transition. The nanostructures were also released from the substrates and their magnetic properties as self-standing nanoparticles investigated. Interesting phenomena on the magnetic behavior of nanoscale FeRh have been elucidated, and the work is also an antecedent for bottom-up nanostructure fabrication of phase transition materials. In this sense, the initial objectives of the thesis are largely fulfilled. Ms. Motyčková demonstrated extraordinary motivation, perseverance, and hard work during her research work. Many of the explored routes were new, and she pioneered procedures that will be very useful in the future. I would like to highlight how she tackled nearly every challenge she was given by accomplishing subsequent tasks of incremental difficulty. During the working process, she developed an increasing sense of independence and intuition to find alternative solutions that would help to advance her research. The thesis manuscript is well-written and contains a remarkably high-quality graphical layout. The presented activities and results are of a high scientific level, original, and relevant in the field of nanomagnetism. For all of the above, I think the diploma thesis deserves the highest mark, A.

Posudek oponenta

Fruchart, Olivier

The Master Thesis is clearly of an overall highest scientific level. The topic assigned has been tackled by an impressive amount of work, covering all aspects from synthesis to physical/magnetic characterization, supported by a not-less impressive range of techniques to bring complementary contribution to scientific knowledge. This care of coverage and support explains that the results gathered definitely bring new insights, although a significant number of investigations have been reported in two decades on low-dimensional FeRh systems. The present work is original and at the state-of-the-art. As a whole, the results are carefully extracted from the experimental data, with a suitable analysis and subsequent modelling. Scientific care is taken to cross-correlate information arising from the various techniques, to come to a single and consistent conclusion. As a minor comment, additional visualization tools could have been used to highlight facets from AFM measurements, such as facet scripts in Gwyddion (mentioned to be used for analysis); this may have allowed a more statistical view on the data than simply a couple of cross-sections. Also, hysteresis loops of FeRh islands could have been discussed more in depth, trying to consider the impact of shape anisotropy on both the saturation field and remanence. All results and formulas are clearly introduced and explained, making the manuscript a suitable reference for any subsequent work. The ordering of the manuscript is perfectly suitable, with a relevant and balance sequence of state-of-the-art to results. Also, I appreciated very much the top quality of the layout, typography and graphics, which are largely above the average of even PhD manuscripts. The use of literature is rather extensive, relevant and useful. As a minor comment, the early works on self-assembly (highlighting the history in the field) could have been included, as here the first dewetting process is mentioned to date back only to 1990 (see Ref.32).

eVSKP id 125430