Orientador: Marcelo Knobel / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-03T22:09:03Z (GMT). No. of bitstreams: 1 Piccin_Rafael_M.pdf: 28985729 bytes, checksum: afa3d6ef86c868ccfd0239d4dfa72438 (MD5) Previous issue date: 2004 / Resumo: Nesta dissertação de mestrado são apresentados resultados do efeito do campo dipolar magnético em conjuntos formados por fios e microfios ferromagnéticos amorfos de composição Fe77,5Sil2,5B15. Devido à estrutura de domínios peculiar destes fios magnéticos, eles podem ser, em princípio, aproximados a dipolos magnéticos, permitido a análise destes campos magnetostáticos nestas estruturas macroscópicas. Os estudos foram realizados em conjuntos de fios colocados lado a lado. As curvas de magnetização foram medidas variando-se o número de elementos. Além disso, no caso de dois fios, medidas em função da separação entre os dois elementos foram realizadas. Estas medidas magnéticas foram feitas empregando um magnetômetro desenvolvido durante o projeto e também utilizado um magnetômetro SQUID. Os resultados são explicados considerando o campo dipolar gerado por cada fio do conjunto, que altera os valores do campo de inversão da magnetização e faz com que platôs sejam observados nas curvas de magnetização. Os efeitos do campo dipolar também foram observados em medidas de magnetoimpedância, onde a presença do fio rico em Fe desloca as curvas de magnetoimpedância de um fio amorfo base Co, de modo análogo a um campo bias / Abstract: The results of the magnetic dipolar field in an array of amorphous ferromagnetic wires and microwires of composition Fe77,5Si12,5B15 are presented in this dissertation. Due to their peculiar domain structure, in principle, they can be approximated to magnetic dipoles, a11owing the analysis of the magnetostatic field among these macroscopic entities. The studies were carried out in arrays of wires placed side by side. The magnetic loops were measured changing the number of elements. Moreover, in the case of two parallel wires, measurements as function of the distance between the wires were performed. The magnetic measurements were carried out in an inductive magnetometer developed during this project and a1so using a SQUID magnetometer. The results are explained considering the dipolar field created by each wire in the array. The dipolar field changes the reversal field of the wires, a11owing the appearance of plateaus during the demagnetization. The effects of the dipolar field were also observed in magnetoimpedance measurements when a Fe-rich wire in placed near an amorphous Co-based wire, its presence dislocates the Co-based wire magnetoimpedance curves, ana1ogously as a bias field / Mestrado / Física / Mestre em Física

Neste trabalho investigamos os efeitos das interações na expansão de um condensado de átomos de Rb. Dois problemas são abordados: o efeito de temperatura finita e as alterações introduzidas pela interação dipolar. No primeiro caso, dados experimentais não puderam ser explicados por meio da aproximação de Thomas-Fermi (TF) no regime de T = 0. Num condensado de cerca de 1 - 2 x 105 átomos condensados, o desvio da aproximação de TF ocorreu pelo fato de termos desconsiderado a interação dos átomos térmicos com os do condensado. Elaboramos um modelo teórico, baseado em modelos existentes de temperatura finita, o qual explicou relativamente bem os nossos resultados experimentais. No segundo problema atacado, foi analisada a variação na expansão do gás condensado quando a interação dipolar é incluída no sistema. Ambos os problemas mostram aspectos importantes da expansão de gases quânticos. / In this study we investigated the effects of interactions on the expansion of a condensate of Rb atoms. Two problems are addressed: the effect of finite temperature and the changes introduced by the dipolar interaction. In the first case, experimental data could not be explained by the Thomas-Fermi (TF) approach in the T = 0 regime. In a condensate of about 1 - 2 x 105 condensed atoms, the deviation of TF approach was due to the fact that we disregarded the interaction of thermal atoms those of the condensate. We developed a theoretical model, based on existing models of finite temperature, which explained relatively well our experimental results. In the second problem considered, we analyzed the variation in the expansion of the condensate gas when the dipolar interaction is included in the system. Both problems show important aspects of the expansion of quantum gases.

Neste trabalho investigamos os efeitos das interações na expansão de um condensado de átomos de Rb. Dois problemas são abordados: o efeito de temperatura finita e as alterações introduzidas pela interação dipolar. No primeiro caso, dados experimentais não puderam ser explicados por meio da aproximação de Thomas-Fermi (TF) no regime de T = 0. Num condensado de cerca de 1 - 2 x 105 átomos condensados, o desvio da aproximação de TF ocorreu pelo fato de termos desconsiderado a interação dos átomos térmicos com os do condensado. Elaboramos um modelo teórico, baseado em modelos existentes de temperatura finita, o qual explicou relativamente bem os nossos resultados experimentais. No segundo problema atacado, foi analisada a variação na expansão do gás condensado quando a interação dipolar é incluída no sistema. Ambos os problemas mostram aspectos importantes da expansão de gases quânticos. / In this study we investigated the effects of interactions on the expansion of a condensate of Rb atoms. Two problems are addressed: the effect of finite temperature and the changes introduced by the dipolar interaction. In the first case, experimental data could not be explained by the Thomas-Fermi (TF) approach in the T = 0 regime. In a condensate of about 1 - 2 x 105 condensed atoms, the deviation of TF approach was due to the fact that we disregarded the interaction of thermal atoms those of the condensate. We developed a theoretical model, based on existing models of finite temperature, which explained relatively well our experimental results. In the second problem considered, we analyzed the variation in the expansion of the condensate gas when the dipolar interaction is included in the system. Both problems show important aspects of the expansion of quantum gases.

Le manuscrit présente des expériences réalisées avec des gaz quantiques de Chrome, un élément présentant un large spin électronique S=3 et des interactions dipolaires non négligeables. Nous avons produit un nouveau gaz quantique, une mer de Fermi avec l'isotope ⁵³Cr, en optimisant la co-évaporation avec l'isotope bosonique, contenant jusqu’à 1000 atomes a T=TF= 0.66± 0.08. Nous avons obtenu de nouveaux résultats sur la thermodynamique d'un condensat de Bose Einstein (CBE) avec degré de liberté de spin. En refroidissant rapidement un gaz thermique multi-composante, nous observons que la dynamique de condensation est affectée par les collisions d'échange de spin. Nous démontrons aussi un nouveau mécanisme de refroidissement, utilisant le degré de liberté de spin, lorsque le CBE est produit dans le niveau de spin de plus basse énergie. Les interactions dipolaires peuplent thermiquement les états de spin excités à bas champ magnétique, et une purification du CBE est obtenue en retirant sélectivement ces atomes. Enfin nous présentons des expériences de dynamique de spin. Dans une première expérience, cette dynamique est obtenue en utilisant un double puits avec des états de spin opposés. Ceci a permis une première mesure d'une des longueurs de diffusion du ⁵²Cr: ɑo = 13.5 ±¹⁵ ₁₀ aB. Nous présentons également des résultats préliminaires dans un piége harmonique et dans un réseau3D. La dynamique de spin est produite par rotation du spin des atomes. La comparaison avecla théorie nous permet de mettre en évidences l'apparition de corrélations quantiques. / This thesis presents experimental results performed with Quantum gases of Chromium atoms. The specificity of Chromium resides in its large electronic spin S=3 and non negligible dipole-dipole interaction (DDI) between atoms. We produced a new quantum gas, a Fermi sea of the ⁵³Cr isotope. Optimization of the co-evaporation with the ⁵²Cr bosonic isotope leads to 10³ atoms at T=TF= 0.66± 0.08. We obtained new results on thermodynamics of a spinor Bose gas. By "shock cooling" a thermal multi-spin component gas, we find that the dynamics of the BEC is affected by spin changing collisions. We also demonstrate a new cooling mechanism based on the spin degrees of freedom when the Bose Einstein condensate (BEC) is in the lowest energy spin state. Dipolar interactions thermally populate spin excited states at low magnetic field. Purication of the BEC is obtained by selectively removing these thermal atoms. Finally, we present spin dynamics experiments. spin following preparation of atoms in a double well trap in opposite stretch spin states allow to measure the last unknown scattering length of ⁵²Cr: ɑo = 13.5 ±¹⁵ ₁₀ ɑB (with ɑB the Bohr radius). We then present preliminary results performed in a 3D lattice and in the bulk, where spin excitation is performed by a spin rotation. We investigate for different experimental congurations which of a theory with or without quantum correlations ts best our data.

Orientadores: Fanny Béron, Kleber Roberto Pirota / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-30T20:53:23Z (GMT). No. of bitstreams: 1 Velo_MuriloFerreira_M.pdf: 6384347 bytes, checksum: 64859a7498ff2d02184a4fff9787d436 (MD5) Previous issue date: 2016 / Resumo: Interações dipolares são amplamente estudadas em magnetismo, devido ao fato de que elas têm um papel fundamental na maioria dos sistemas magnéticos. Porém, para vários sistemas, o cálculo das interações magnetostáticas é feito de duas maneiras: considerando-se apenas o primeiro termo da expansão multipolar e/ou aproximando as entidades magnéticas por dipolos perfeitos. Neste trabalho iremos realizar este cálculo de maneira exata, através da expansão multipolar, considerando a forma geométrica da entidade magnética. Para tal montamos um sistema macroscópico bidimensional composto por agulhas magnéticas de bússola, no qual foi automatizado a aquisição de imagens e o controle de campo magnético. No objetivo de verificar a exatidão do nosso cálculo, implementamos uma simulação utilizando o método de Monte Carlo para comparar com os resultados experimentais. Focamos o estudo sobre sistemas de duas e cinco agulhas, sendo que o primeiro permite a comparação com a solução analítica exata do problema. Observamos que a introdução dos termos de ordem mais alta na expansão multipolar modifica o potencial magnético gerado por uma agulha de bússola. A expansão multipolar do potencial mostrou que devemos considerar termos de ordem l = 1, 3 e 5, sendo que os termos de ordem par são nulos e termos l ? 7 são desprezíveis. A simulação de Monte Carlo reproduziu com fidelidade o comportamento dos sistemas experimentais, mostrando uma boa concordância entre as curvas de histerese simuladas e experimentais. Explicamos os resultados a partir do fato que a expansão multipolar introduz mínimos locais nos diagramas de energia de interação de duas partículas com campo magnético aplicado nulo. Estas regiões são conhecidas como os pontos de equilíbrio metaestáveis de um sistema magnético. Para um sistema de duas agulhas, descrevemos como os saltos na curva de histerese estão relacionados com descontinuidades na trajetória no espaço de fases de energia do sistema, criadas pelos termos de ordem mais alta. Dos nossos resultados, concluímos que para descrevermos o comportamento magnético de um sistema de agulhas de bússola, devemos levar em conta termos de ordem mais alta na expansão multipolar, bem como a geometria desta entidade / Abstract: Dipolar interactions are widely studied in magnetism, since they play a key role in most magnetic systems. However, for several systems the magnetostatic interactions calculation is done through two ways: considering only the multipole expansion first term and/or approximating the magnetic entities as perfect dipoles. In this work we will perform this calculation exactly, through the multipole expansion, considering the magnetic entities geometric shape. For such, we set up a two-dimensional macroscopic system made of magnetic compass needles, where we automated the image acquisition and the magnetic field control. In the objective of verifying our calculation accuracy, we implemented a simulation using the Monte Carlo¿s method to compare with the experimental results. We focused the study on systems of two and five needles, since the first one allowing comparing with the experimental results. We observed that the introduction of higher order terms in the multipole expansion modifies the magnetic potential generated by a compass needle. The multipole expansion showed that we need to consider order terms of l = 1, 3 and 5, with nulls even terms are and terms of l ? 7 are negligible. The Monte Carlo simulation accurately reproduced the experimental systems behaviors, exhibiting a good agreement between the simulated and experimental hysteresis curves. We explained the results through the fact that the multipole expansion introduces local minima in the two magnetic particles interaction energy diagrams with null applied magnetic field. These regions are known as metastable equilibrium points in a magnetic system. For a two-needle system, we described in detail how the hysteresis curve drops are related to trajectory discontinuities in the system energy phase space, created by the higher order terms. From our results, we conclude that to describe the magnetic behavior of a compass needle system, one must take into account higher order terms in the multipole expansion, as well as the entity geometry / Mestrado / Física / Mestre em Física / 1374983/2014 / CAPES

Orientador: Marcelo Knobel / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-30T18:13:51Z (GMT). No. of bitstreams: 1 OrozcoHenao_JuanManuel_M.pdf: 7687296 bytes, checksum: d9aecf2d118aed0c43ab747d0dcff34c (MD5) Previous issue date: 2016 / Resumo: Nanopartículas de magnetita com diâmetros entre 5nm e 19nm sintetizadas mediante um método de decomposição térmica são apresentadas. A caracterização estrutural é feita usando diferentes técnicas experimentais como a microscopia eletrônica de transmissão (TEM), difração de raios-X e espalhamento de raios-X a baixos ângulos (SAXS) de onde são obtidos os tamanhos e a forma das nanopartículas. As propriedades magnéticas e de magneto-hipertermia das nanopartículas são estudadas para diferentes parâmetros de produção como concentração dos surfactantes, temperaturas de refluxo e atmostfera de crescimento. A dependência com a temperatura das propriedades magnéticas são analisadas dentro do marco do modelo usual do superparamagnetismo e o modelo de interação superparamagnética (ISP), de onde os parâmetros magnéticos dependentes do tamanho como anisotropia magnética (1.06x10^4 J/m^3 até 9.91x10^4 J/m^3), momento magnético por partícula (2618?B até 11500?B), temperatura de bloqueio (18K até mais de 300K) e energia de ineração dipolar magnética (0.55x10^-21 J até 5.5x10^-21 J) são inferidos. Os resultados de magneto-hipertermia foram obtidos mediante a medição da resposta térmica das nanopartículas de magnetita suspendidas em tolueno. Valores da taxa de absorção específica (SAR) são calculados experimental e teoricamente utilizando a teoria de resposta linear para um sistema superparamagnético não interagente. Valores de SAR entre 3.0W/g e 40.3W/g e a sua dependência com a frequência e o campo aplicado são apresentados. Como resultado interessante, a resposta de magneto-hipertermia para as nanopartículas de 19nm preparadas na presença de oxigênio e mais de 10 vezes maior do que nanopartículas similares mas obtidas na ausência da atmosfera de oxigênio. Também é destacada a possibilidade de prever a resposta de magneto-hipertermia num sistema de nanopartículas magnéticas mediante a obtenção dos parâmetros de caracterização magnetica e estrutural / Abstract: Magnetite nanoparticles with diameters between 5nm and 19nm synthesized by means of a thermal decomposition method are presented. Structural characterization is made by different experimental techniques such as transmission electron microscopy (TEM), X-ray diffraction and Small Angle X-ray Scattering (SAXS) from where nanoparticles size and shape are obtained. Magnetic and magneto-hyperthermia properties of the nanoparticles are studied for different production parameters, such as surfactant concentrations, refluxing temperature and growth atmosphere. Temperature dependence of the magnetic properties are analyzed in the framework of the standard superparamagnetism model and the interacting superparamagnetic model (ISP), from where size dependent magnetic parameters for each sample such as anisotropy (1.06×10^4 J/m^3 to 9.91x10^4 J/m^3) magnetic moment per particle (2618?B to 11500?B), blocking temperature (18K to above 300K) and magnetic dipolar interaction energy on dried nanoparticle samples (0.55 × 10^?21 J to 5.5 × 10^?21 J) are inferred. Magneto-hyperthermia results are obtained by measuring the thermal response of magnetite nanoparticles dissolved in toluene. Specific absorption rate (SAR) values are theoretically and experimentally calculated by means of a linear response theory approach of a non-interacting superparamagnetic system. SAR values between 5.8W/g and 40.3W/g are reported; interestingly, the magneto-hyperthermia response for 19nm nanoparticles prepared in presence of an oxygen atmosphere is more than 10 times larger than similar particles obtained in absence of oxygen atmosphere. Also it is important to highlight the possibility to obtain the magneto-hyperthermia behavior of a magnetic nanoparticles system by knowing a priori its structural and magnetic characterization parameters / Mestrado / Física / Mestre em Física / 1247647/2013 / CAPES

Dans ce mémoire nous présentons plusieurs études expérimentales des propriétés magnétiques d’un condensat de Bose-Einstein de Chrome chargé dans un réseau 3D, en nous focalisant sur les effets associés aux interactions dipolaires. Nous montrons que dans un réseau 3D, la relaxation dipolaire est un processus résonant du fait de la réduction de la densité d’états orbitaux accessibles. Les résonances sont observées à des champs magnétiques Bres tels que l’énergie Zeeman relâchée soit égale à l’énergie nécessaire à exciter les atomes dans une bande d’énergie supérieure du réseau. Nous pouvons inhiber ce processus en appliquant un champ différent de Bres. L’analyse des résonances a permis de sonder la structure de bande 3D du réseau, ainsi que la mise en évidence de l’effet des interactions entre atomes. Nous avons étudié la dynamique d’échange de spin dans un réseau 3D. Nous présentons en particulier la première observation d’échange de spin entre atomes localisés dans des sites séparés. Ces études permettent une exploration nouvelle du magnétisme en réseau. En variant la profondeur du réseau, nous étudions ces effets dans le régime superfluide, bien décrit par une théorie de champ moyen, et dans le régime fortement corrélé, dont la description théorique est difficile. Enfin, nous étudions l’évolution de deux spins géants interagissant par interaction dipolaire. Le condensat initialement divisé en deux, les atomes des deux nuages sont préparés dans des états de spin opposés formant ainsi deux spins géants ±3xN. Nous montrons que toute dynamique de spin est énergétiquement inhibée pour de grands spins ce qui est bien reproduit par une théorie classique. / This Thesis reports on several experimental studies of magnetic properties of a Chromium Bose-Einsteincondensate loaded into a 3D optical lattice, focusing on the effects induced by dipolar interactions.We show that in a 3D lattice dipolar relaxation is a resonant process due to the reduction of the density ofaccessible orbital states. These resonances are observed for magnetic fields Bres such that the Zeeman energyreleased matches an excitation towards higher-energy bands of the lattice. We can thus inhibit those processes byapplying a field different from Bres. Analyses of the resonances allowed us to probe the lattice 3D band structureas well as to demonstrate the effects of local interactions between atoms.We study spin exchange dynamics in a 3D lattice. We especially observed for the first time spin exchangebetween atoms localized in different lattice sites mediated by dipolar interactions. These studies are the firststep toward a new exploration of magnetism in lattice. Varying the depth of the lattice we study these effects inthe superfluid regime, well described by mean filed theories, as well as in the strongly correlated regime, whosetheoretical description is still challenging.Finally, we study the evolution dynamics of two giant spins interacting through dipolar interactions. Thecondensate being initially splitted in half, atoms from the two clouds are prepared in opposite spin states thusproducing two giant spins ±3×N. We show that any spin dynamics is energetically inhibited for large spinswhich is well accounted for by a classical theory

This PhD thesis presents a study of structure-composition correlations of bioactive glasses (BGs) by employing solid-state Nuclear Magnetic Resonance (NMR) spectroscopy. Silicate-based Na2O−CaO−SiO2−P2O5 BGs are utilized clinically and are extensively investigated for bone regeneration purposes. Once implanted in the human body, they facilitate bone regeneration by partially dissolving in the body fluids, followed by the formation of a biomimetic surface-layer of calcium hydroxy-carbonate apatite (HCA). Eventually, the implanted BG totally integrates with the bone. The bioactivity of melt-prepared BGs depends on their composition and structure, primarily on the phosphorus content and the average silicate-network connectivity (NC). We explored these composition-structure relationships for a set of BGs for which the NC and phosphorus contents were varied independently. The short-range structural features of the glasses were explored using 29Si and 31P magic-angle-spinning (MAS) NMR spectroscopy. 31P MAS NMR revealed that the orthophosphate content is directly proportional to the total P content of the glass, with a linear correlation observed between the orthophosphate content and the silicate network connectivity. The bearings of the results for future BG design are discussed. By using multiple-quantum coherence-based 31P NMR experiments, the spatial distribution of orthophosphate groups was probed in the melt prepared BGs, as well as in two mesoporous bioactive glasses prepared by an evaporation-induced self-assembly technique. The results evidence randomly distributed orthophosphate groups in the melt-prepared BGs, whereas the pore-walls of the mesoporous bioactive glasses constitute nanometer-sized clusters of calcium phosphate. The distribution of Na+ ions among the phosphate/silicate groups were studied by heteronuclear dipolar-based 23Na−31P NMR experiments, verifying that sodium is dispersed nearly randomly in the glasses. The phosphorus and proton environments in biomimetically grown HCA were investigated by using 1H and 31P MAS NMR experiments. Our studies revealed that the biomimetic HCA shared many local structural features with synthetic and well-ordered hydroxy-apatite. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Accepted.</p>

Doctor of Philosophy / Department of Physics / Talat S. Rahman / In this work we present a study of the geometric, electronic, vibrational and magnetic properties of several nanostructured systems for which experimental data call for a theoretical understanding. In order to investigate the effect of magnetic dipolar interactions on the magnetization of nanomagnets arranged in finite lattices, we utilize a phenomenological classical approach, which is based on the Landau-Lifshitz equation. Dipolar interactions lead to hysteretic behavior of the magnetization curves and established that the external field sweep rate, sample temperature, and shape anisotropy play a role in determining the specifics. Our results (derived from a classical approach) for magnets arranged in a square lattice suggest that stepped hysteresis curves do not have necessarily a quantum origin (quantum tunneling of the magnetization). We also find that in the square lattice small changes in the dipolar strength introduce sudden transitions in the magnetic hysteresis. For the examination of geometric vibrational and electronic structure of systems of interest, we turn to density functional theory (DFT), which is the leading technique for modeling nanoscale systems from first principles. We have applied DFT to either address some old queries of surface science, such as the dynamics of the CO-chemisorbed Cu(001) surface, or to contribute to the forefront of hydrogen-based economy through the comprehension of the growth and diffusion of Pt islets on Ru(0001), or to predict the geometric and electronic properties of materials to-be-created, as in the case of core-shell bimetallic nanoclusters. In the case of CO on Cu(001), although the bond has been considered to be weak enough so as to treat the adsorbate and substrate separately, our calculations are able to reproduce measurements and provide evidence that the dynamics of the molecule is influenced by the substrate and vice versa, as well as by intermolecular interactions. Taking into account the adsorbate-substrate interplay, has furthermore clarified issues that were pending for the clean surface and led to the correct interpretation of some features in the phonon dispersion of the chemisorbed surface. DFT has also directed us to the conclusion that the catalytic properties of few-atom Pt islets on Ru nanoclusters are preserved by the low probability of these islets to diffuse through the edges of the Ru nanoclusters. Moreover, the analysis of the Ag_{27}Cu_7 nanoalloy from ab initio methods has opened a wide panorama in terms of the geometry, coordination, energetics, and electronic structure of alloyed phases, in general,that may aid in the assembling on new materials.

Cette thèse présente une étude de films monomoléculaires d'acides gras à l'interface eau-air, principalement par microscopie à l'angle de Brewster. Cette technique permet l'observation directe des coexistences de phases lors de transitions de phases du premier ordre; de plus elle est sensible à l'anisotropie optique des films. La première partie contient une étude du diagramme de phase des acides gras, qui comporte des mésophases analogues aux phases de cristaux liquides smectiques. Nous avons montré que lors des transitions de phases entre phases denses, la texture (l'arrangement moléculaire)des phases est réversible et nous avons obtenu des informations sur l'ordre des transitions. Nous avons aussi mis en évidence, dans deux phases constituées de molécules verticales, une très faible anisotropie optique due à la forme rectangulaire du réseau moléculaire. Nous avons ensuite étudié une film d'acide myristique adsorbé à la surface d'une solution aqueuse d'acide myristique. Nous avons observé des domaines d'une mésophase "inclinée" contenant des lignes de défauts d'orientationmoléculaire présentant des fluctuations thermiques. La mesure de leur amplitude a permis de déterminer la tension de ces lignes. Nous nous sommes aussi intéressés aux constantes élastiques qui gouvernent la forme et la texture à l'équilibre des domaines de mésophase. Nous avons d'une part déterminé la tension de ligne de l'interface entre une phase liquide et une mésophase "inclinée" en étudiant la forme des domaines. Celle-ci résulte de l'équilibre entre la tension de ligne, qui favorise des domaines circulaires, et les interactions répulsives à longue portée entre dipoles moléculaires, qui forment les domaines. Des mesures de potentiel de surface ont permis de calculer l'intensité des forces dipolaires. d'autre part, la texture d'autre domaines de cette mésophaseinclinée nous a renseigné sur la valeur du rapport entre l'élasticité de courbure de la direction moléculaire et l'anisotropie de la tension de ligne.