|
|
Magnetic force microscopy and transport properties of metamagnetic nanostructures
Jaskowiec, Jiří ; Vaňatka, Marek (referee) ; Uhlíř, Vojtěch (advisor)
Iron-rhodium (FeRh) is a material featuring a first-order phase transition between antiferomagnetic (AF) and feromagnetic (FM) phases. The phase transition is symmetric with respect to the direction of transition in bulk FeRh and FeRh thin films. The bachelor thesis focuses on the properties of mesostructures of sub-micron size, where asymmetry between the AF-FM and FM-AF transitions has been recently discovered using electrical transport measurements dependent on temperature. The phase domain structure of FeRh mesostructures during the phase transition is visualized by magnetic force microscopy (MFM) in an out-of-plane magnetic field. Quantitative analysis of the measured magnetic signal reveals the effect of structure size on supercooling of the FM phase and abrupt increase of the AF phase during the FM-AF transition.
|
|
|
Transport properties of one dimensional magnetic nanostructures
Holobrádek, Jakub ; Liška, Jiří (referee) ; Vaňatka, Marek (advisor)
Magnetic nanowires have been recently under the scope for their specic properties and applications in microelectronics and sensors. This work deals with measurement of transport properties of nanowires in magnetic field. Nanowires prepared in the range of the thesis were grown by the physical vapor deposition method in colaboration with the University of Technology Sydney. The main task of the thesis was to develop a process of contacting single nanowires by electron beam lithography and measuring them using anisotropic magnetoresistance in angle dependent magnetic field. Characterization techniques such as transmission electron microscopy, energy-dispersive X-ray spectroscopy and magnetic force microscopy were used to provide further analysis.
|
|
|
Spin vortex states in magnetostaticaly coupled magnetic nanodisks
Vaňatka, Marek ; Hrabec, Aleš (referee) ; Urbánek, Michal (advisor)
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 multilayers for spintronics applications
Vaňatka, Marek ; Dvořák, Petr (referee) ; Urbánek, Michal (advisor)
Magnetic multilayers have applications as magnetic field sensors or magnetic memory cells. Mastering the methods of fabrication and characterization of the structures such as spin valve or magnetic tunnel junction is an important step towards more complicated spintronics devices. This work summarizes basic theory of magnetism, magnetotransport properties, and it describes basic applications of magnetic multilayers. The experimental part of this work deals with the sample preparation by ion beam sputtering (IBS), ion beam assisted deposition (IBAD), and characterization of prepared multilayers by measuring anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), or tunnel magnetoresistance (TMR).
|
guest ::
