The continued progress of modern information technology relies on understanding the influence of magnetic anisotropy on magnetic thin films. In this work, two sources of magnetic anisotropy are examined in two different soft ferromagnets: a uniaxial anisotropy induced during the fabrication of Ni80Fe20 and exchange anisotropy, or exchange bias, which occurs at the interface of Ni77Fe14Cu5Mo4/Fe50Mn50 bilayer. A home-built Magneto-optical Kerr effect magnetometer is used to measure the magnetic response of the soft ferromagnetic films and details of its construction are also discussed. A simple model of uniaxial anisotropy is described, then applied, to the uniaxial NiFe film and deviations from the model are critically analyzed. The exchange bias and coercive fields of NiFeCuMo/FeMn are reported for the first time and studied as a function of buffer layer material. The influence of the different buffer layer materials on the magnetization response of the bilayer is explained from a structural standpoint.

Articial spin ice structures are two-dimensional systems of lithographically fabricated lattices ofelongated ferromagnetic islands, which interact via dipolar interaction. These systems have beenshown to be a suitable playground to study the magnetic, monopole-like, excitations, similar tothose in three-dimensional rare-earth pyrochlores. Therefore, such articial structures can be potentialmaterials for investigations of magnetricity [1]. The investigations of these articial spin icestructures stretches from the direct imaging of the magnetic congurations among the islands to indirectinvestigation methods allowing to determine the phase transitions occurring in such systems. Inthis project, square articial spin ice arrays were investigated employing magneto-optical Kerr eectfor the measurement of the magnetic susceptibility. The susceptibility dependence on temperaturewas measured at dierent frequencies of the applied AC magnetic eld for arrays of the dierentisland spacing and at two dierent incident light directions with the respect to the direction of theislands. A peak shift of the real part of susceptibility, χ', with increasing frequency towards thehigher temperatures was observed. Furthermore, a rough estimation of the relaxation times of themagnetic moments in the islands is given by the analysis of the susceptibility data.

We present a time-resolved Kerr microscope, capable of measuring the magnetization dynamics of samples grown on transparent, double-side-polished substrates.The magnetization is excited by a current pulse, using a coplanar waveguide placed beneath the samples. The Kerr rotation is detected with the stroboscopic pump-probe technique, using a probing laser, synchronized with the current pulse.We report benchmark measurements of the time-resolved Kerr instrument for magnetization dynamics in thin permalloy and FePd films. The experimental results for ferromagnetic resonance peaks have been compared with the values predicted by Kittel. / Vi presenterar ett tidsupplöst Kerr-mikroskop, kapabel till att mäta magnetiseringsdynamiken hos magnetiska prov tillverkade på transparenta, dubbelsdigt polerade substrat. Magnetiseringen exiteras med en strömpuls via en koplanär vågguide placerad under provet. Kerr-rotationen detekteras med hjälp av en stroboskopisk ”pump-probe” teknik som använder en ”probing” laser synchroniserad med strömpulsen. Vi rapporterar prestandatest av det tidsupplösta kerr-instrumentet för magnetiseringsdynamiken i tunna permalloy - och FePd - filmer. De experimentella resultaten för de ferromagnetiska resonans-peakarna har jämförts med beräknade värden från Kittel.

The goal of this project was to study some unexplored optical and magneto-optical properties of the newest member of III-V ferromagnetic structures, InMnSb, as well as InSb films and InSb/AlInSb quantum wells. The emphasis was on dynamical aspects such as charge and spin dynamics in order to address several important issues of the spin-related phenomena. The objectives in this project were to: 1) understand charge/spin dynamics in NGS with different confinement potentials, 2) study phenomena such as interband photo-galvanic effects, in order to generate spin polarized current, 3) probe the effect of magnetic impurities on the spin/charge dynamics. This thesis describes three experiments: detection and measurement of spin polarized photocurrents in InSb films and quantum wells arising from the circular photogalvanic effect, and measurements of the carrier and spin relaxation in InSb and InMnSb structures by magneto-optical Kerr effect and differential transmission. The samples for our studies have been provided by Prof. Heremans at Virginia Tech, Prof. Santos at the University of Oklahoma, and Prof. Furdyna at the University of Notre Dame. / Ph. D.

This thesis aims to explore the effect of in situ ion gun etching on magnetic proper- ties, such as perpendicular magnetic anisotropy, of Pt/Co/Pt multilayers. Perpendicular magnetic anisotropy is of interest due to its importance in spintronic application. Calibration spectroscopic ellipsometry measurements of Pt and Co layers to obtain sputter yields of respective magnetron targets were performed as a first step. After that, ten Pt/Co/Pt multilayers with different Co and top Pt layer thicknesses were prepared. Five of these samples were etched by the ion gun, mounted inside of the magnetron chamber, during different stages of the deposition. To characterize the prepared samples, experimental and modeled Kerr rotation spectra were confronted. This provided an insight into the cross-sections of the investigated samples. Magnetic hysteresis loops measured by vibrating sample magnetometer and Kerr rotation setup demonstrated higher coercive field and change of the slope of the loop induced by ion etching. When compared to the obtained cross-sections, a correlation between the change of magnetic loops and intermixing of Pt and Co at the interface was visible. This intermixing was higher in samples treated by the ion gun. 1

Magneto-optical materials such as permalloy can be used to create artificial spin- ice (ASI) lattices with antiferromagnetic ordering. Magneto-optical materials used to create diffraction lattices are known to exhibit magnetic scattering at the half- order Bragg peak while in the ground state. The significant drawbacks of studying the magneto-optical generation of OAM using x-rays are cost, time, and access to proper equipment. In this work, it is shown that the possibility of studying OAM and magneto-optical materials in the spectrum of visible light at or around 2 eV is viable. Using spectroscopic ellipsometry it is possible to detect a change in the magnetization of thin permalloy films with thicknesses between 5 and 20 nm. Patterns consistent with OAM were found at 1.95 eV using a square lattice with a 4𝜋 radial phase shift in the antiferromagnetic ground state. Evidence of magnetic scattering at the half-order Bragg peak using 1.95 eV was also found.

Title: Magnetic nanostructures for recording and optical sensors Author: Eva Lišková Department: Institute of Physics, Charles University Supervisor: Prof. Ing. Štefan Višňovský, DrSc. Abstract: Magneto-optical (MO) spectra of multilayered structures with enhanced MO effect were studied using the polar and longitudinal Kerr spectroscopy with oblique angle of light incidence in the photon energy range 1.2 eV to 5 eV. The samples with Fabry- Perot cavity like architecture, were modeled using Yeh matrix formalism. Two sets of samples, with composition FeF2/Fe/FeF2 and AlN/Fe/AlN, were prepared by molecular beam epitaxy and sputtering. The relations were studied between the position of the enhanced peak in the MO spectra and the structure. Second part of this work was devoted to the Pt/Co/Pt structures and the influence of the ion implantation on MO spectra and structural composition. The studied multilayer structures present interest for MO sensor and memory applications. Keywords: Magneto-optical Kerr effect, Magneto-optical sensor, Fabry-Perot resonator, Ion implantation

Made available in DSpace on 2014-12-17T15:14:57Z (GMT). No. of bitstreams: 1 EdimilsonFS_DISSERT.pdf: 2546760 bytes, checksum: 08525df56e96d75f8d221757342883b4 (MD5) Previous issue date: 2012-02-17 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / In this work, we investigated the magnetic properties of a monocrystalline Fe thin film and of Fe(80 ?)/Cr(t)/Fe(80 ?) tri-layers, with the nonmagnetic metallic Cr spacer layer thickness varying between 9 ? < t < 40 ?. The samples were deposited by the DC Sputtering on Magnesium Oxide (MgO) substrates, with (100) crystal orientation. For this investigation, experimental magneto-optical Kerr effect (MOKE) magnetometry and ferromagnetic resonance (FMR) techniques were employeed. In this case, these techniques allowed us to study the static and dynamical magnetization properties of our tri-layers. The experimental results were interpreted based on the phenomenological model that takes into account the relevant energy terms to the magnetic free energy to describe the system behavior. In the case of the monocrystalline Fe film, we performed an analytical discussion on the magnetization curves and developed a numerical simulation based on the Stoner-Wohlfarth model, that enables the numerical adjustment of the experimental magnetization curves and obtainment of the anisotropy field values. On the other hand, for the tri-layers, we analyzed the existence of bilinear and biquadratic couplings between the magnetizations of adjacent ferromagnetic layers from measurements of magnetization curves. With the FMR fields and line width angular dependencies, information on the anisotropy in three layers was obtained and the effects of different magnetic relaxation mechanisms were evidenced. It was also possible to observe the dependence of the epitaxy of the multilayers with growth and sputtering parameters. Additionally it was developed the technique of AC magnetic susceptibility in order to obtain further information during the investigation of magnetic thin films / Nesta disserta??o investigamos as propriedades magn?ticas de um filme monocristalino de ferro e tricamadas com a composi??o Fe(80?)/Cr(t)/Fe(80?), variando as espessuras da camada met?lica n?o magn?tica separadora (Cr) entre 9? < t < 40?. As amostras foram depositadas pela t?cnica Sputtring DC sobre substrato de ?xido de Magn?sio (MgO) com orienta??o cristalina (100). Para esta investiga??o foram utilizadas as t?cnicas experimentais de magnetometria por efeito Kerr Magneto-?ptico (MOKE) e Resson?ncia Ferromagn?tica (FMR). Estas t?cnicas permitiram o estudo das propriedades est?ticas e din?micas da magnetiza??o das multicamadas. Os resultados experimentais foram interpretados com base no modelo fenomenol?gico que leva em considera??o os termos mais relevantes da energia livre magn?tica para descrever o comportamento do sistema. Para o filme monocristalino de ferro, realizamos uma discuss?o anal?tica das informa??es das curvas de magnetiza??o e desenvolvemos uma simula??o num?rica baseada no modelo de Stoner-Wohlfarth, possibilitando o ajuste num?rico das curvas de magnetiza??o experimentais e a obten??o do valor de campo de anisotropia. Para as tricamadas, analisamos a presen?a dos acoplamentos bilinear e biquadr?tico entre as magnetiza??es das camadas ferromagn?ticas adjacentes a partir das medidas das curvas de magnetiza??o. Com as depend?ncias angulares do campo de FMR e da largura de linha obtivemos informa??es sobre as anisotropias presentes nas tricamadas e evidenciamos os efeitos de diversos mecanismos de relaxa??o magn?tica. Tamb?m foi poss?vel observar a depend?ncia da epitaxia das multicamadas com os par?metros de crescimento do Sputtering. Adicionalmente foi desenvolvida, durante o per?odo do mestrado, a t?cnica de susceptibilidade magn?tica AC com o objetivo de obter resultados inovadores na investiga??o de filmes finos magn?ticos

Made available in DSpace on 2014-12-17T15:15:00Z (GMT). No. of bitstreams: 1 CharlieSG.pdf: 1382454 bytes, checksum: 2b54a2a0dcd81f1ca374af1328ff8c73 (MD5) Previous issue date: 2006-03-15 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / n this master s dissertation a Kerr Magneto Optic s magnetometer effect was set up to do characterization of samples type films fine and ultra thin, these samples will be grown after the implementation of the sputtering technique at the magnetism laboratory of of this department. In this work a cooled electromagnet was also built the water and that it reaches close values to 10kOe with a gap of 22 mm including an area of uniform field of 25mm of diameter. The first chapter treats of the construction of this electromagnet from its dimensioning to the operation tests that involve measures of reached maximum field and temperature of the reels when operated during one hour. The second chapter is dedicated to the revision of the magnetism and the magnetization processes as well as it presents a theoretical base regarding the magnetic energies found in films and magnetic multilayer. In the sequence, the third chapter, is especially dedicated the description of the effects magneto opticians the effect kerr in the longitudinal, traverse and polar configurations, using for so much only the classic approach of the electromagnetism and the coefficients of Fresnel. Distinguished the two areas of observation of the effect regarding thickness of the film. The constructive aspects of the experimental apparatus as well as the details of its operation are explained at the room surrender, also presenting the preliminary results of the measures made in one serializes of permalloy films and concluding with the results of the characterization of the first films of iron and permalloy grown here at the theoretical and experimental physics department at UFRN / Nesta disserta??o de mestrado foi montado um magnet?metro de efeito Kerr Magneto-?ptico para fazer caracteriza??o de amostras tipo filme fino e ultrafino, amostras estas que ser?o crescidas ap?s a implementa??o da t?cnica de Sputtering no laborat?rio de magnetismo deste departamento. Neste trabalho tamb?m foi constru?do um eletro?m? arrefecido a ?gua e que atinge valores pr?ximos a 10 kOe com um gap de 22 mm abrangendo uma regi?o de campo uniforme de 25 mm de di?metro. O primeiro cap?tulo trata da constru??o deste eletro?m? desde o seu dimensionamento at? os testes de opera??o que envolvem medidas de campo m?ximo alcan?ado e temperatura das bobinas quando operando durante 1 hora. O capitulo 2 ? dedicado a uma revis?o do magnetismo e dos processos de magnetiza??o bem como apresenta uma base te?rica a respeito das energias magn?ticas encontradas em filmes e multicamadas magn?ticas. Na seq??ncia, o terceiro cap?tulo, ? dedicado a descri??o dos efeitos magneto ?pticos em especial o efeito kerr nas configura??es longitudinal, transversal e polar, utilizando para tanto somente a abordagem cl?ssica do eletromagnetismo e os coeficientes de Fresnel. Distinguindo em seguida, as duas regi?es de observa??o do efeito referentes a espessura do filme. Os aspectos construtivos do aparato experimental bem como os detalhes de sua opera??o s?o explanados no quarto capitulo, apresentando tamb?m os resultados preliminares das medidas efetuadas em uma serie de filmes de Permalloy e finalizando com os resultados da caracteriza??o dos primeiros filmes de ferro e Permalloy crescidos aqui no departamento de f?sica te?rica e experimental da UFRN

This thesis is divided into three main sections that deal with optical and magnetic thin films properties and their measurements techniques. Principles of the spectroscopic reflectometry and measurements of optical properties are described in the first part. Results of imaging reflectometry are most important. This technique is based on in situ monitoring of optical properties of SiO2 thin films during etching over the area cca 10 × 13 mm2. In next section magnetic properties of thin films and new apparatus built on the Institute of Physical Engineering of BUT are shown. Magnetic properties were observed by longitudinal magneto-optical Kerr effect. The construction of the device is based on a light beam with rectilinear polarization reflected from magnetic material with turned polarization. For investigation of local magnetic properties of microstructures a microscope objective focusing laser beam on the sample is used. The last part of the thesis is aimed on improving of a spin valve structure Co/Cu/NiFe. This work was done within the frame of the Erasmus project in Laboratoire Louis Néel in Grenoble. The goal was to achieve the value of GMR (Giant Magnetoresistance) as high as possible by changing of deposition parameters. This value describes the rate of resistances in different mutual directions of magnetization in trilayers.