Master's Thesis
Spin vortex states in magnetostaticaly coupled magnetic nanodisks
Final Thesis 8.24 MBAuthor of thesis: Ing. Marek Vaňatka, Ph.D.
Acad. year: 2014/2015
Supervisor: Ing. Michal Urbánek, Ph.D.
Reviewer: Ing. Aleš Hrabec, Ph.D.
Abstract:Magnetic vortices in ferromagnetic disks are curling magnetization structures characterized by the sense of the spin circulation in the plane of the disk and by the direction of the magnetization in the vortex core. Concepts of memory devices using the magnetic vortices as multibit memory cells have been presented, which brought the high demand for their research in many physical aspects. This work investigates the magnetostatic coupling in pairs of ferromagnetic disks to clarify the influence of nearby disks or other magnetic structures to the vortex nucleation mechanism. To ensure that the vortex nucleation is influenced only by the neighbouring magnetic structures, the randomness of the nucleation process was studied in single disks prior to the work on pairs of disks. We had to ensure that the vortex nucleation is influenced only by the neighbouring magnetic structures and not by an unwanted geometrical asymmetry in the studied disk. Lithographic capabilities were inspected in order to achieve the best possible geometry. Further we present a concept of electrical readout of the spin circulation using the anisotropic magnetoresistance, which allows automated measurements to provide sufficient statistics. To explain the magnetoresistance behaviour, numerical calculations together with magnetic force microscopy measurements are presented.
magnetic vortex, circulation switching, magnetoresistance, magnetic force microscopy
Date of defence
22.06.2015
Result of the defence
Defended (thesis was successfully defended)
Grading
A
Language of thesis
Czech
Faculty
Department
Study programme
Applied Sciences in Engineering (N3901-2)
Field of study
Physical Engineering and Nanotechnology (M-FIN)
Composition of Committee
prof. RNDr. Tomáš Šikola, CSc. (předseda)
prof. RNDr. Miroslav Liška, DrSc. (místopředseda)
prof. RNDr. Bohumila Lencová, CSc. (člen)
prof. RNDr. Jiří Komrska, CSc. (člen)
prof. RNDr. Petr Dub, CSc. (člen)
prof. RNDr. Radim Chmelík, Ph.D. (člen)
prof. RNDr. Jiří Spousta, Ph.D. (člen)
prof. Ing. Ivan Křupka, Ph.D. (člen)
prof. RNDr. Pavel Zemánek, Ph.D. (člen)
RNDr. Antonín Fejfar, CSc. (člen)
Supervisor’s report
Ing. Michal Urbánek, Ph.D.
Grade proposed by supervisor: A
Reviewer’s report
Ing. Aleš Hrabec, Ph.D.
Grade proposed by reviewer: A