Author of thesis: Ing. Oleksii Zadorozhnii
Acad. year: 2020/2021
Supervisor: Ing. Vojtěch Uhlíř, Ph.D.
Reviewer: Ing. Oldřich Schneeweiss, DrSc.
Abstract:Exchange bias is an intriguing physical phenomenon occuring at the interface of antiferromagnet (AF) and ferromagnet (FM) materials, which has already been widely applied in electronics and magnetic recording industry. Despite being intensely studied for a long time, the exact mechanism behind it remains an unsettled matter. This work presents an overview of the relevant studies documenting exchange bias in thin film bilayer systems, including both experimental evidence and theoretical models developed. The experimental tasks of this diploma thesis covered both manufacturing and measurement of different exchange bias model systems. An Fe/FeRh bilayer (here the FeRh layer features a phase transition from AF to FM at 360K), provides convenient tunability of the exchange bias. Next, the exchange bias and shape anisotropy effects were investigated in Fe/FeRh microstructures. Lastly, the presence of exchange bias was investigated between the coexisting FM and AF phases in submicron FeRh nanowires. The samples were fabricated using magnetron sputtering and E-beam lithography. All the presented systems were analyzed using Magneto-Optical Kerr Effect microscopy. Exchange bias was successfully found in the Fe/FeRh system nearly identical in magnitude and orientation to the results in literature, having an inferior FM-AF interface quality. Training effect as well as rotational asymmetry were also proven to exist within this system, solidifying the presence of exchange bias. In nanowires, significant exchange bias was measured between the coexisting FM and AF phases during cooling from the FM phase to the AF phase.
exchange bias, exchange anisotropy, unidirectional anisotropy, training effect, FeRh, metamagnetic, nanowires, bilayers, thin film, magnetism, phase coexistence
Date of defence
14.06.2021
Result of the defence
Defended (thesis was successfully defended)
Grading
A
Process of defence
Po otázkách oponenta bylo dále diskutováno: Morfologie připravených nanostruktur. Zobrazení nejistot měření v grafech. Student otázky zodpověděl.
Language of thesis
English
Faculty
Department
Study programme
Physical Engineering and Nanotechnology (N-FIN-P)
Composition of Committee
prof. RNDr. Tomáš Šikola, CSc. (předseda)
prof. RNDr. Miroslav Liška, DrSc. (místopředseda)
prof. RNDr. Petr Dub, CSc. (člen)
prof. RNDr. Radim Chmelík, Ph.D. (člen)
doc. Ing. Radek Kalousek, Ph.D. (člen)
prof. RNDr. Jiří Komrska, CSc. (člen)
prof. RNDr. Pavel Zemánek, Ph.D. (člen)
doc. Mgr. Adam Dubroka, Ph.D. (člen)
prof. Mgr. Dominik Munzar, Dr. (člen)
RNDr. Antonín Fejfar, CSc. (člen)
prof. RNDr. Jiří Spousta, Ph.D. (člen)
doc. Ing. Stanislav Průša, Ph.D. (člen)
Supervisor’s report
Ing. Vojtěch Uhlíř, Ph.D.
Grade proposed by supervisor: A
Reviewer’s report
Ing. Oldřich Schneeweiss, DrSc.
Grade proposed by reviewer: A