Optical and Magneto-Optical Spectroscopy of Magnetic Nanostructures.

Jana Hamrlová

Disertační práce

Anotace:

Prezentujeme metodu separace magnetick´ych pˇr´ıspˇevk˚u k mˇeˇren´emu magneto-optick´emu jevu od r˚uzn´ych magnetick´ych materi´al˚u (nebo magnetick´ych vrstev) obsaˇzen´ych v nanostruktuˇre. Metoda je zaloˇzena na v´ypoˇctu singul´arn´ıho rozkladu. Metodu jsme pouˇzili na separaci hysterezn´ıch smyˇcek magneticky tvrd´ych ˇc´astic Fe a magneticky mˇekk´e slitiny FeNbB v povrchov´e vrstvˇe FeNbB p´ask˚u vyroben´ych metodou rychl´eho chlazen´ı taveniny na rotuj´ıc´ım v´alci a k urˇcen´ı objemov´e koncentrace Fe ˇc´astic v povrchov ´e vrstvˇe p´asku na stranˇe dot´ykaj´ıc´ı se chlazen´eho kola. Metodu jsme d´ale pouˇzili k separaci hysterezn´ıch smyˇcek ˇctyˇr multivrstevn´ych blok˚u v (TbFe/Si3N4)4 struktuˇre z mˇeˇren´ı pol´arn´ıch magneto-optick´ych spekter. Pro pouˇzit´ı t´eto metody k separaci kvadratick´eho magneto-optick´eho jevu jsme urˇcili ˇctyˇri z´akladn´ı spektra (nemagnetickou permitivitu ε(0), element K popisuj´ıc´ı line´arn´ı magneto-optick´y tenzor a elementy G44 a G11 − G12 popisuj´ıc´ı kvadratick´y magneto-optick´y tenzor) z ab-initio v´ypoˇct˚u tenzoru permitivity v kubick´ych krystalech bcc Fe, bcc Co a fcc Ni. Tato z´akladn´ı spektra popisuj´ı magneto-optick´e efekty do druh´eho ˇr´adu v magnetizaci vˇcetnˇe pro libovolnou orientaci vzorku a libovoln´y smˇer magnetizace.

Abstract:

We present the method of separating the magnetic contributions to the measured (MO) effect from several magnetic materials (or several magnetic layers) contained in nanostructure. The method is based on singular value decomposition. We use the method to separate hysteresis loops of hard magnetic Fe particles and soft magnetic FeNbB alloy on wheel side of as-quenched FeNbB ribbons and to determine the volume fraction of Fe particles in the surface layer of the ribbon. Then we use the method to separate the hysteresis loops of four ferromagnetic layers from a (TbFe/Si3N4)4 multilayer stack structure using the spectroscopy measurements of polar magneto-optical effect. In order to extend this method to separate the measured MO effect quadratic in magnetization, we have determined the four principal spectra (the permittivity ε(0) unperturbed by magnetization, the element K describing linear magneto-optical tensor and the elements G44 and G11−G12 describing quadratic magneto-optical tensor) from ab-initio calculations of the permittivity tensor of cubic bcc Fe, fcc Co, and fcc Ni, which fully describe the magneto-optical effects up to second order in magnetization for arbitrary sample’s orientation and arbitrary magnetization direction.

Klíčová slova

magnetooptick´y Kerr˚uv jev (MOKE), hloubkov´a a materi´alov´a citlivost, reverzace magnetizace, magnetizaˇcn´ı jevy druh´eho ˇr´adu, argumenty symetrie, kubick´e krystaly, TbFe multivrstvy, FeNbB p´asky

Keywords

magneto-optical Kerr effect (MOKE), depth and material selectivity, magnetization reversal, second-order effects in magnetization, symmetry arguments, cubic crystals, TbFe multilayers, as-quenched FeNbB ribbons

Jazyk práce: angličtina

Datum vytvoření / odevzdání či podání práce: 3. 9. 2014

Obhajoba závěrečné práce

• Obhajoba proběhla 3. 2. 2015
• Vedoucí: Kamil Postava
• Oponent: Jan Peřina, Jan Šik, Jaroslav Vlček

VŠB - Technická univerzita Ostrava

Hornicko-geologická fakulta

Doktorský studijní program / obor:
Fyzika / Aplikovaná fyzika