FePt-based thin films: doping with 3d and 4f elements

  • L10 - chemically ordered FePt thin films with large perpendicular magnetic anisotropy (PMA) of up to 7 MJ/m^3 are one of the most promising materials to overcome existing limitations in data storage density. It has been recently implemented as ultra-high density magnetic storage media for applications in heat-assisted magnetic recording (HAMR) and is of high interest for other spintronic applications, exchange-coupled systems, magnetic random access memories, rare earth free magnets. The development of new technologies will persist further to meet the demands of data growth and higher read-write rates. In this regard, ultrafast all-optical switching of magnetization has the potential to be a future technology of magnetic recording devices. Hence, the design of new magnetic materials, e.g. tuning of FePt properties to make it accessible for AOS, are of high interest from a fundamental as well as a technological point of view. In this thesis different concepts of tuning theL10 - chemically ordered FePt thin films with large perpendicular magnetic anisotropy (PMA) of up to 7 MJ/m^3 are one of the most promising materials to overcome existing limitations in data storage density. It has been recently implemented as ultra-high density magnetic storage media for applications in heat-assisted magnetic recording (HAMR) and is of high interest for other spintronic applications, exchange-coupled systems, magnetic random access memories, rare earth free magnets. The development of new technologies will persist further to meet the demands of data growth and higher read-write rates. In this regard, ultrafast all-optical switching of magnetization has the potential to be a future technology of magnetic recording devices. Hence, the design of new magnetic materials, e.g. tuning of FePt properties to make it accessible for AOS, are of high interest from a fundamental as well as a technological point of view. In this thesis different concepts of tuning the properties of FePt thin films were explored using various established experimental techniques in order to take advantage of the remarkable magnetic properties of FePt for AOS. This work is dedicated to the development of a controlled way to change the material properties of FePt, in particular, to stabilize a ferrimagnetic order. In the first part of the results, rapid thermal annealing (RTA) was employed to induce the A1 to L10 phase transformation in FePt/Mn/FePt trilayers. The dependence of magnetic and structural properties on the annealing temperature and Mn concentration was investigated. The formation of a ternary alloy, only partially doped with Mn, and diffusion of Mn to the surface during the RTA process was discovered. This resulted in a gradient of Mn concentration throughout the film and the formation of the oxide at the free surface. The second part of this thesis is dedicated to ion implantation. Tb was chosen as a dopant to reduce the net magnetization and to tune the effective damping in L10 - FePt films. This study includes the evaluation of the disordering process, induced by ion implantation at 10 keV, and its effect on static and dynamic magnetic properties. The main part of the experimental results is focused on epitaxially grown FePt thin films doped with different 3d and 4f elements. It includes a comparison of two rare-earth dopants, Tb and Gd, which couple antiferromagnetically to the Fe moments, resulting in the formation of speri- and ferrimagnetic systems. Depending on concentration and deposition temperature, large rare-earth atoms amorphize their local atomic environment and introduce a temperature-dependent magnetic anisotropy. By contrast, the addition of 3d transition metals such as Cr, Mn, and Cu allows substituting Fe at the L10 lattice sites. All three elements affect PMA and morphology of the film depending on concentration, which results in reduced coercivity and Curie temperature. In the case of Cr and Mn, which couple their magnetic moments antiparallel to Fe, a transition from ferro- to ferri- and to antiferromagnetic order is observed.show moreshow less

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Metadaten
Author:Nataliia SchmidtORCiD
URN:urn:nbn:de:bvb:384-opus4-820122
Frontdoor URLhttps://opus.bibliothek.uni-augsburg.de/opus4/82012
Advisor:Manfred Albrecht
Type:Doctoral Thesis
Language:English
Year of first Publication:2020
Publishing Institution:Universität Augsburg
Granting Institution:Universität Augsburg, Mathematisch-Naturwissenschaftlich-Technische Fakultät
Date of final exam:2020/12/04
Release Date:2021/04/29
Tag:FePt alloys; Transition-metal rare-earth alloys; Magnetic order; Magnetic anisotropy; Magnetic thin films
GND-Keyword:Platinlegierung; Dünne Schicht; Magnetische Anisotropie; Strukturelle Phasenumwandlung; Magnetische Datenspeicherung; Eisenlegierung
Institutes:Mathematisch-Naturwissenschaftlich-Technische Fakultät
Mathematisch-Naturwissenschaftlich-Technische Fakultät / Institut für Physik
Mathematisch-Naturwissenschaftlich-Technische Fakultät / Institut für Physik / Lehrstuhl für Experimentalphysik IV
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik
Licence (German):Deutsches Urheberrecht