HRDINOVÁ, S. Vliv epitaxního napětí na koexistenci feromagnetické a antiferomagnetické fáze na bočním rozhraní mezi tenkou vrstvou a proužkem FeRh [online]. Brno: Vysoké učení technické v Brně. Fakulta strojního inženýrství. 2024.

Posudek vedoucího

Zadorozhnii, Oleksii

During the course of this bachelor thesis the student has shown great interest in the topic, high degree of enthusiasm and was very adaptible and quick-learning. Unfortunately due to delays on our part with the lithographic procedure, student had very limited time to conduct the experiments on 180 nm thick films. However, for the short time spent on the Magnetic Force Microscopy we consider the experimental output to be of very high quality.  Theoretical and state of the art parts of this thesis in my opinion cover all the necessary basics for understanding of metamagnetism in FeRh, phase transition phenomena as well as the influence of the strain on the phase transition. Interpretation of the results was made difficult due to FeRh supercooling coming into play, which was discovered for 10 micrometre sized elements after the entire set of measurements was made. This made interpretation of the results more difficult than expected, however the conclusions of the thesis are still valid and applicable for our future measurements, and definitely provide useful information on strain influence on FeRh phase transition from antiferromagnetic to ferromagnetic state.  With the above factors mentioned, we consider that within given parameters the student has performed very close to the best expectations and provided us with very valuable data as part of their bachelor's thesis.

Posudek oponenta

Kepič, Peter

The thesis starts very nicely. The author clearly describes a basic theory of magnetism and consistently shifts to classifying magnets with relevant graphs describing them. This graph is later well-used when introducing iron-rhodium alloy, an antiferromagnetic to ferromagnetic phase-change material. While phase transition is adequately described using a visually explicit phase diagram, a more detailed description of the hysteresis with a focus on heating and cooling temperatures is missing. Especially later in the state-of-the-art section, where the supercooling of nanostructures is revealed, and comparison to thin film/bulk temperatures is crucial. Moreover, switching between degrees of Celsius and Kelvins in the text makes understanding harder. The methods section is adequately brief. However, there is a slight imbalance between the first two methods (Magnetron and VSM) and AFM. While AFM is, in my opinion, overexplained, Magnetron and VSM especially miss a more detailed description of operation. In the last section, I admire the huge amount of samples the author measured and the work she did. Sadly, weaker interpretation of results and sentence arrangement make it hard to understand these results and their impact. Specifically, nanostructures are sometimes called nanowires, other times strips or stripes; results from images are followed by a discussion about fabrication/methods and then back to other results without explaining the meaning of previous results; FM and AFM contrasts are not adequately explained; therefore clusters and AFM domains discussed in the text are not visible (at least for me; should be highlighted). Despite the weaker interpretation on which the author should work in the future, I evaluate this thesis as very good, especially when considering the amount of time and work she had to dedicate during her bachelor year to study the problematics and measure the samples.

eVSKP id 160975