Conselho Nacional de Desenvolvimento Científico e Tecnológico / Anisotropic magnetoresistance (AMR) consists in the change of the resistivity of a ferromagnetic metal as a function of the angle between the current and the magnetization, what makes AMR-based sensors promising to measure both angular and linear positions. These devices usually have a structure of Ta/Ni81Fe19/Ta and the thickness of the Ni81Fe19 layer is about 10 nm so as to reduce the demagnetization field parallel to surface. In order to acquire high magnetic field sensitivity (S) and low Barkhausen noise the films should have high AMR values (ΔDR=R) and low coercivity. However, during fabrication, the structures are often exposed to temperatures above 200oC, what changes the characteristics of the interfaces and reduces ΔDR=R. On the other hand, ΔDR=R and S can be remarkably enhanced by insertion of nano-oxide layers that act like difusion barriers on the interfaces. The enhancement is mainly attributed to the large electron specular reflection at the flatter interfaces. In this work we have proposed to verify the possibility of enhance ΔDR=R and S in structures with good thermal stability just by adding an oxidation step after growthing each layer, forming TaOx. We studied the influence of the deposition parameters in the structural and magnetic properties of the samples and otimized the growth of thin films of Ni81Fe19 by magnetron sputtering. We also verified the influence of the annealing in the structural properties of nanostructures of Ta/Ni81Fe19/Ta exposed or not to oxidation on the interfaces. We observed that the TaOx nano-oxide layer can work as expected, however the poor cristalinity of the Ni81Fe19 layers leads to AMR values lower than the literature ones. / Magnetorresistência anisotrópica (AMR) consiste na variação da resistividade de um metal ferromagnético como uma função do ângulo entre a corrente e a magnetização, o que faz com que sensores que utilizam este efeito sejam promissores para medidas de posição tanto angulares quanto lineares. Estes dispositivos normalmente possuem a estrutura Ta/Ni81Fe19/Ta com a espessura da camada de Ni81Fe19 sendo da ordem de 10 nm, para reduzir o campo desmagnetizante paralelo à superfície. Para obter alta sensibilidade (S) e baixos níveis de ruído Barkhausen os filmes devem apresentar alta variação percentual da AMR (ΔDR=R) e baixa coercividade. Entretanto, durante o processo de fabricação as estruturas frequentemente são expostas à temperaturas maiores que 200oC, o que pode alterar as características das interfaces e reduzir ΔDR=R. Por outro lado, ΔDR=R e S podem ser significativamente incrementados através da inserção de nanocamadas de óxidos que atuam como barreiras contra difusão nas interfaces. O aumento é atribuído ao maior nível de reflexões eletrônicas especulares nas interfaces mais lisas. Neste trabalho, propomos verificar se é possível aumentar ΔDR=R e S para estruturas com boa estabilidade térmica simplesmente acrescentando uma etapa de oxidação após o crescimento de cada camada, pela formação de TaOx. Estudamos a influência dos parâmetros de deposição nas propriedades estruturais e magnéticas das amostras e otimizamos o crescimento de filmes finos de Ni81Fe19 pela técnica de magnetron sputtering. Verificamos também a influência do tratamento térmico nas propriedades estruturais de nanoestruturas do tipo Ta/Ni81Fe19/Ta submetidas ou não à oxidação das interfaces. Observamos que a nanocamada de TaOx pode desempenhar o papel esperado, todavia a qualidade cristalina das camadas de Ni81Fe19 acarretou em valores quantitativos de ΔDR=R menores que os encontrados na literatura.

Made available in DSpace on 2015-03-03T15:15:29Z (GMT). No. of bitstreams: 1 CristovaoPNJ_DISSERT.pdf: 20191942 bytes, checksum: ddd5466a16c8a26b044b5c940b443f3c (MD5) Previous issue date: 2013-06-18 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The ferromagnetic materials play an important role in the development of various electronic devices and, have great importance insofar as they may determine the efficiency, cost and, size of the devices. For this reason, many scientific researches is currently focused on the study of materials at ever smaller scales, in order to understand and better control the properties of nanoscale systems, i.e. with dimensions of the order of nanometers, such as thin film ferromagnetic. In this work, we analyze the structural and magnetic properties and magnetoresistance effect in Permalloy-ferromagnetic thin films produced by magnetron sputtering. In this case, since the magnetoresistance effect dependent interfaces of thin films, this work is devoted to the study of the magnetoresistance in samples of Permalloy in nominal settings of: Ta[4nm]/Py[16nm]/Ta[4nm], Ta[4nm]/Py[16nm]/O2/Ta[4nm], Ta[4nm]/O2/Py[16nm]/Ta[4nm], Ta[4nm]/O2/Py[16n m]/O2/Ta[4nm], as made and subjected to heat treatment at temperatures of 160?C, 360?C e 460?C, in order to verify the influence of the insertion of the oxygen in the layer structure of samples and thermal treatments carried out after production of the samples. Results are interpreted in terms of the structure of the samples, residual stresses stored during deposition, stresses induced by heat treatments and magnetic anisotropies / Os materiais ferromagn?ticos exercem um papel importante no desenvolvimento de diversos dispositivos eletr?nicos e t?m grande import?ncia na medida que os mesmos podem determinar a efici?ncia, o custo e o tamanho dos dispositivos. Por este motivo, muitas das investiga??es cient?ficas t?m, atualmente, se concentrado no estudo de materiais em escalas cada vez menores, a fim de entender e controlar melhor as propriedades dos sistemas nanosc?pios, ou seja, com dimens?es da ordem de 10?9 m, tais como filmes finos ferromagn?ticos. Nesse trabalho, s?o analisadas as propriedades estruturais e magn?ticas e o efeito da magnetorresist?ncia em filmes finos ferromagn?ticos de Permalloy produzidos por magnetron sputtering. Neste caso, visto que o efeito da magnetorresist?ncia ? dependente das interfaces dos filmes finos, este trabalho ? dedicado ao estudo da magnetorresist?ncia em amostras de Permalloy com configura??es nominais de: Ta[4nm]/Py[16nm]/Ta[4nm], Ta[4nm]/Py[16nm]/O2/Ta[4nm], Ta[4nm]/O2/Py[16nm]/Ta[4nm], Ta[4nm]/O2/Py[16n m]/O2/Ta[4nm], na condi??o de como feitas e submetidas a tratamentos t?rmicos com temperaturas de 160 C, 360 C e 460 C, a fim de verificar a influ?ncia da inser??o das camadas de O2 na estrutura das amostras e de tratamentos t?rmicos realizados ap?s a produ??o das amostras. Os resultados obtidos s?o interpretados em termos da estrutura das amostras, tens?es residuais armazendas durante a deposi??o, tens?es induzidas pelos tratamentos t?rmicos e anisotropias magn?ticas.

Amostras policristalinas de La(5/8-y)Pr(y)Ca(3/8)MnO(3); 0 y 0.625; foram produzidas pelo método da mistura estequiométrica de óxidos e tratadas termicamente ao ar a 1400 oC. As amostras foram caracterizadas através de medidas de difração de raios-X, resistividade elétrica rho(T), susceptibilidade magnética chi(T) e magnetorresistividade rho(T, H = 50 kOe). Os resultados das análises dos diagramas de raios-X indicaram que os materiais são de fase única e que houve uma substituição efetiva de La por Pr no sítio A ao longo da série. Medidas de rho(T) e chi(T) revelaram que a temperatura de transição de fase metal-isolante TMI e temperatura de Curie TC decrescem com o aumento da concentração y e que a resistividade residual rho0 (rho(T = 10 K)) é consideravelmente alta em amostras com y 0.35. Ainda, com o decréscimo de T, as amostras com y 0.35 transitam para uma fase de ordenamento de carga em TOC ~ 194 K e, em seguida, para uma fase metálica em TMI. Essas medidas também sugerem a coexistência de fases ferromagnética-metálica FMM e de ordenamento de carga isolante OCI nesses materiais. Nas propriedades físicas macroscópicas, a fase FMM mostrou ser a dominante para os compostos com pequenas concentrações de Pr (y 0.25) e a fase OCI dominante para os compostos com altas concentrações de Pr (y 0.40). As medidas de rho(T, H = 50 kOe) mostram que a magnitude da resistividade elétrica decresce drasticamente nas vizinhanças de TMI sob a aplicação de um campo magnético externo. A magnitude de MR (MR = (rho(H = 0)-rho(H = 50 kOe))/rho(H = 50 kOe)) entre os extremos da série (y = 0 e 0.625) varia até sete ordens de grandeza, sendo que o máximo valor de MR para amostras com y = 0 é de ~ 0.75 e naquelas com y = 0.625 é ~ 3.4x106 . O diagrama de fases deste composto evidencia uma região crítica (0.30 y 0.40) onde os valores de TMI, TC, MR e 0 variam abruptamente como função de y, sendo que em outras regiões tal variação é mais suave. A variação significativa desses quatro valores indica uma competição mais forte entre as fases coexistentes ocorre na região crítica. Algumas características marcantes podem ser observadas nas amostras da região crítica tais como: a presença de um segundo pico, abaixo de TMI, em ~ 90 K e ~ 72 K na curva de rho(T) de amostras com y = 0.30 e 0.35, histerese térmica mais pronunciada em rho(T) e chi(T), MR torna-se colossal, relaxação significativa da resistividade elétrica com o tempo, entre outras. Assim, as propriedades de transporte e magnéticas nessa região crítica são dominadas pela forte competição entre as fases coexistentes. / Polycrystalline samples of La(5/8-y)Pr(y)Ca(3/8)MnO(3); 0 y 0.625; were synthesized by the solid-state reaction method and sintered in air at 1400 oC. These compounds were studied by measurements of X-ray powder diffraction, magnetic susceptibility chi(T), and electrical resistivity rho(T, H). X-ray powder diffraction measurements indicated single phase materials and an effective substitution of La by Pr. Results from rho(T) and chi(T) revealed that increasing y in this series results in a rapid reduction of both the insulator to metal transition temperature TMI and the Curie temperature TC. Such a rapid decrease in TMI with increasing y is also accompanied by the occurrence of a new transition temperature, termed TCO, which is related to the transition to the charge ordered CO state. Such a temperature, which is essentially independent of y, occurs at TCO ~ 194 K and is mainly observed in samples with y 0.35. The other feature is the presence of a large residual resistivity electrical rho(0 = (10 K)) for large y (y 0.35) at low-T even though rho(T) suggests a metallic behavior below TMI. The temperature for the maximum magnetoresistance effect occurs near TMI, that shifts to higher T with increasing field. The MR is defined here as (rho(H = 0)-rho(H = 50 kOe))/rho(H = 50 kOe) and is enhanced by seven orders of magnitude from ~ 0.75 up to ~ 3.4x106 in samples with y = 0 and y = 0.625, respectively. Some features like the thermal hysteresis observed in both rho(T) and chi(T) curves indicate the coexistence of different phases in a range of y concentration, i. e., the ferromagnetic-metallic FMM and the charge ordered-insulating COI domains. The FMM is stable for y 0.25, but the COI state becomes dominant for y 0.40. There is a critical region in the phase diagram, ranging from y = 0.30 to 0.40, where the magnitude of the TMI, TC, MR, and 0 were found to display abrupt changes with increasing y. Some anomalous features like a second peak in rho(T) below TMI, a two-step increasing in chi(T), a colossal MR effect and others are observed for compositions belonging to this critical region. Our combined data suggest that the general physical properties of these compounds in such a critical region are dominated by the strong competition between coexisting ferromagnetic-metallic and charge ordered-insulating phases.

No description available.

Le but de la thèse sera d'étudier la faisabilité d'un nouveau procédé de nanostructuration des jonctions tunnel de dimension sub-30nm récemment imaginé et breveté par Spintec et le LTM et de tester les propriétés des jonctions tunnel obtenus sur les plans structural, magnétique et des propriétés électriques. Une attention particulière sera mise sur la caractérisation des défauts générés en bord de piliers lors de la gravure des jonctions tunnels et l'impact de ces défauts sur les propriétés magnétiques et de transport. Une autre partie de la thèse concerne l'optimisation des propriétés magnétiques et de transport des empilements jonctions tunnel magnétiques en vue d'en améliorer la stabilité thermique, l'amplitude de magnétoresistance tunnel et la facilité de gravure de l'empilement.En particulier l'insertion de nouveaux matériaux réfractaires (W, ) dans les empilements a été étudiée pour améliorer la stabilité de l'empilement lors des recuits à haute température. Des améliorations ont également été apportées pour renforcer la stabilité de la couche de référence de la jonction tunnel lorsque cette dernière est située au dessus de la barrière tunnel. Par ailleurs, une nouvelle couche de couplage antiferromagnétique a été mise au point permettant de réduire significativement l'épaisseur totale de l'empilement et par là même facilitant sa gravure.Tous ces résultats ont été obtenus par des mesures magnétiques et de transport réalisées sur les couches continues et sur des piliers de taille nanométriques. / The first aim of the thesis is to study the feasibility of a new process for nanopatterning of sub-30nm diameter tunnel junctions recently patented by Spintec and LTM and to test the properties of tunnel junctions obtained, from the point of view of magnetic and electrical properties. Particular attention will be paid on the characterization of defects generated at the pillar edges when patterning the tunnel junctions and the impact of these defects on the magnetic and transport properties. Another part of the thesis is focused on improving the magnetic and transport MTJ stacks with higher thermal budget tolerance. As a part of this, new materials (W, etc) were used as cap layer or as a spacer layer in composite free layer of pMTJ stacks. Moreover, different magnetic materials combined with different non-magnetic spacer have been investigated to improve the thermal stability factor of the composite storage layers. Detailed structural characterizations were performed to demonstrate the improvements in magnetic and electrical properties. A new RKKY coupling layer was found which allowed to obtain an extremely thin pMTJ stack by reducing the SAF layer thickness to 3.8nm. Seed lees multilayers with enhanced PMA is necesssary to realize a top-pinned pMTJ stack which is necessary to configure a spin-orbit torque MRAM (SOT-MRAM)stack and double magnetic tunnel junction stacks (DMTJs). A new seed less multilyar with enhanced PMA and subsequently advanced stacks such as conventional-DMTJ, thin-DMT, SOT-MRAM stacks, Multibit memory were realized. Finally, electrical properties patterned memory devices were also studied to correlate with the magnetic properties of thin films.

Magnetické materiály a z nich vyrobené nanostruktury jsou v průběhu posledních let studovány pro jejich aplikace v např. záznamových médiích a logických obvodech. Tato práce navazuje na náš předchozí výzkum tohoto oboru s hlavním zaměřením na statické a dynamické vlastnosti nanostrukturovaných magnetických materiálů, jako například NiFe, CoFeB a YIG. Práce začíná teoretickým úvodem s popisem mikromagnetických systémů, dynamiky magnetických vortexů, feromagnetické rezonance (FMR) a spinových vln včetně jejich disperzních vlastností. Následuje popis použitých experimentálních metod a první experimentální část zabývající se nukleačním procesem magnetického vortexu, jinými slovy procesem transformace ze saturovaného stavu do spinové konfigurace magnetického vortexu v průběhu snižování magnetického pole. Jsou použity mikroskopické metody zobrazující magnetickou strukturu materiálu, jmenovitě Lorentzova transmisní elektronová mikroskopie a rentgenová transmisní mikroskopie. Výsledky jsou poté korelovány s měřením elektrické odezvy pomocí jevu anizotropní magnetorezistence. Výhodou elektrických měření je, že plně elektrická detekce dovoluje použití tohoto systému v uzavřených systémech integrovaných obvodů. Výsledky oblasti nukleací magnetických vortexů ukazují, že při tomto procesu prochází magnetizace v nano- a mikrometrových magnetických discích několika fázemi s růsnými typy spinových konfigurací nazvaných nukleační stavy. Dále je představeno měření magnetických materiálů pomocí vektorového síťového analyzátoru (VNA), což je aplikováno na měření resonance magnetických vortexů (určení gyrotropické frekvence a měření vysokofrekvenčních módů), feromagnetické rezonance tenkých vrstev (získání základních magnetických materiálových parametrů) a spektroskopii spinových vln. Právě spektroskopie spinových vlna je rozvinuta za účelem měření disperzních relací tenkých magnetických vrstev, což je základní charakteristika, jejíž znalost je důležitá v návrhu aplikací. Nakonec je představeno anténní zařízení, díky kterému lze oddělit magnetické buzení od vzorku samotného bez nutnosti absolvovat proces elektronové litorafie, což je zapotřebí v klasickém přístupu antény na vzorku a kontaktování vysokofrekvenční sondou. Toto zařízení se skládá ze skleněného kantilívru, na kterém je vyrobena budící anténa, konektoru a spojovacího prvku v podobě plošného spoje. Celé zařízení je díky umístění na x-y-z stolek s náklonem pozicovatelné a lze tedy měřit v jakémkoliv místě vzorku. Umístění antény na sklo umožňuje navigaci pomocí mikroskopu a optické měření, např. metodou Brillouinova světelného rozptylu (BLS) nebo Kerrova jevu.

Random number generation can be based on physical events with probabilistic character, or on algorithms that use complex or one-way functions, alternatively on both of these approaches. A magnetic vortex is a basic state of magnetization that forms in magnetic micro- and nanostructures of an appropriate shape, dimensions and material. Quantities of the magnetic vortex form randomly if ambient conditions are chosen eligibly. A concept of a true random number generator using a random switching of states of the magnetic vortex is presented in this thesis. This concept is realized and random numbers were experimentally generated and numbers were statistically analysed.

Nanoelectronics and spintronics are concerned with writing, transporting, and reading information stored in electronic charge and spin degrees of freedom at the nanoscale. Past few years have shown that two spintronics effects discovered in the 19th century, namely anisotropic magnetoresistance and anomalous Hall effect, can be used also for sensing antiferromagnetism which opened the field of antiferromagnetic spintronics. The more than a century of controversial studies of these effects have shown their relativistic spin-orbit coupling and spin-polarisation symmetry breaking origin. However, a complete understanding of these effects and a fully predictive theory capable of identifying novel suitable antiferromagnetic materials are still lacking. Here, by extending modern symmetry and topology concepts in condensed matter physics, we have further developed the theory of anisotropic magnetoresistance and spontaneous Hall effect. Our approach is based on magnetic symmetry and topology analysis of antiferromagnetic energy bands, Bloch spectral functions, and Berry curvatures calculated from the state-of-the- art first-principle theory. This guided us to the prediction of two novel, previously unanticipated effects: relativistic metal-insulator transition from antiferromagnetic Dirac fermions, and crystal Hall...

Perovskit-Oxide weisen eine große Bandbreite an physikalischen Eigenschaften bei gleichzeitig hoher struktureller Qualität in kleinsten Dimensionen auf. Die dramatischen Veränderungen ihrer Eigenschaften bei nur geringer Variation der stöchiometrischen Zusammensetzung sind sowohl für ein tieferes physikalisches Verständnis als auch für mögliche Anwendungsperspektiven interessant. In der vorliegenden Arbeit wurde der Einfluss von Ladungsübertragung an Grenz- flächen, Anisotropiemodifikation durch Verspannung und Oberflächeneffekte sowie magnetische und strukturelle Kopplung untersucht. Aufgrund ihrer kontrastierenden Eigenschaften im Hinblick auf Ferromagnetismus und Ladungstransport wurden dotiertes Lanthanmanganat und Strontiumruthenat (SRO) für die Untersuchungen ausgewählt. Durch ihre hervorragenden Wachstumseigenschaften mit fehlerlosen Grenzflächen auf atomarer Ebene erlauben sie als Modellsystem die Untersuchung elektronischer, magnetischer und struktureller Kopplung in Perovskit-Oxiden – mit folgenden Ergebnissen: Durch Ladungsübertragung an Grenzflächen wird Ferromagnetismus in Schichten von weniger als vier Einheitszellen in Manganaten stabilisiert. Die mikroskopische Struktur der Systeme kann aus der Analyse der durch die Anisotropie bedingten Symmetrie der winkelabhängigen Magnetotransport- messungen erschlossen werden. Bei abnehmender Schichtdicke verringert sich die intrinsische orthorhombische Symmetrie in SRO zugunsten einer tetragonalen aufgrund der Symmetriebrechung an der Grenzfläche. Die Untersuchungen des anormalen Hall Effekts unterstreichen seine Tensor-Natur und zeigen eine Abhängigkeit des Vorzeichens sowohl von der magnetischen Anisotropie als auch der mikroskopischen Schichtqualität. Die Beobachtung einer Anisotropie oberhalb der Übergangstemperatur von SRO in Manganatschichten einer Dicke von zwei bis sechs Einheitszellen weist auf eine strukturelle Kopplung über die Sauerstoffoktaederrotationen hin. Die komplexe Wechselwirkung zwischen antiferromagnetischer Kopplung und schichtdickenabhängiger Anisotropie und dem magnetischen Moment werden in einem 2-Schichten-Modell beschrieben. Übergitter mit Einzelschichten von weniger als drei Einheitszellen lassen sich nicht mehr mit individuellen Einzelschichten beschreiben sondern stellen einen künstlichen Ferrimagneten dar. / Perovskite oxides show a range of physical properties in combination with high structural quality in small dimensions. The dramatic change of their properties upon small variation in stoichiometry or external influences as pressure/strain are interesting for both a deeper understanding of fundamental condensed matter physics as well as electronic applications. In the present thesis the influence of charge transfer at interfaces, modification of the magnetic anisotropy by strain and surface effects, as well as magnetic and structural coupling was studied. In virtue of their contrasting ferromagnetic and transport properties, charge doped lanthanum manganite and strontium ruthenate (SRO) were chosen for this study. Their superior growth properties allowing atomically flat defect free interfaces make them a model system to study electronic magnetic and structural coupling phenomena in perovskite oxides − with the following findings: Charge transfer at interfaces stabilizes ferromagnetism in single layers of manganites down to one unit cell thickness similar to finite size scaling in ordinary transition metal ferromagnets. The microscopic structure of crystalline layers can be obtained from an analysis of the symmetries present in angle dependent magnetotransport measurements, which are determined by the anisotropy. Upon thickness reduction, the intrinsic orthorhombic symmetry in SRO is reduced in favour of a tetragonal one owing to the symmetry breaking at the interface. Studies on the anomalous Hall effect underline its tensorial nature and show a sign dependence on both magnetic anisotropy and microstructural quality. The observation of an in-plane anisotropy in manganite layers in the thickness range of two to six unit cells indicates a structural coupling via the oxygen octahedra. The complex interplay of antiferromagnetic coupling and layer thickness dependent anisotropy and magnetic moment are described in a bilayer model. Superlattices with individual layers of less than three unit cells cannot be described by the individual layer properties but represent an artificial ferrimagnet.

Magnetoresistive effects are powerful tools for studying the intricate structure of solid state electronic systems, and have many applications in our current information technology. In particular, the electronic system reflects the crystal symmetry and the orbital structure of the atoms of a given solid, and thus is crucial to understanding magnetism, superconductivity and many other effects which are of key interest to current solid state research. Consequently, studies of the electrical transport properties of solid state matter allow to evaluate this imprint and in turn draw conclusions about the interactions within a material. In this thesis, we will exploit the capabilities of magnetotransport measurements to infer the properties of a multitude of magnetic systems. In turn, this allows us to push the understanding of transport phenomena in magnetic materials. The first part of this work is focused on the magnetoresistance observed in spin Hall active metals in contact with a magnetic insulator. In such bilayers, the interfacial spin accumulation caused by the spin Hall effect in the metal can interact with the magnetic insulator, giving rise to interesting magnetoresistive effects. In the framework of this thesis, bilayers with several magnetic insulators are studied, including antiferomagnets, ferrimagnets and paramagnets (disordered magnets). For the disordered magnetic insulators, we find that the established spin Hall magnetoresistance framework does not allow to consistently describe the observed transport response. Consequently, we propose an alternative explanation of the magnetoresistance in such heterostructures, using the Hanle magnetoresistance and assuming an interface which has a finite electrical conductivity. This alternative model can serve to generalize the theory of the spin Hall magnetoresistance, providing addition information on the microscopic picture for the loss of the transverse spin component. Additionally, by partly removing the magnetic insulator and studying the ensuing changes, we verify that magnons are crucial for the observation of a non-local magnetoresistance in bilayers of a magnetic insulator and a metal. Finally, the local and non-local spin Seebeck effect (i.e. the electric field generated by a thermally driven pure spin current) is investigated in bilayers of Cr2O3 and Pt where the occurrence of a spin superfluid ground state was reported. In our sample, however, the transport response is consistent with the antiferromagnetic spin Seebeck effect mediated by the small magnetic field induced magnetization also reported for other antiferromagnet/metal heterostructures. As such, we cannot verify the presence of a spin superfluid ground state in the system. In the second part of this thesis, the topological properties of the electronic system and the related changes of the magnetoelectric and magnetothermal transport response are investigated. To that end, we first demonstrate a novel measurement technique, the alternating thermal gradient technique, allowing to separate the relevant thermovoltages from spurious other voltages generated within the measurement setup. We employ this novel technique for measuring the topological Nernst effect in Mn 1.8 PtSn and show the possibility to combine the magnetoelectric and magnetothermal transport response to evaluate the presence of topological transport signatures without requiring magnetization measurements. Additionally, we show that the anomalous Nernst effect in the non-collinear antiferromagnet Mn3Sn is connected to the antiferromagnetic domain structure: Using spatially resolved measurements of the anomalous Nernst effect, direct access to the antiferromagnetic domain structure is demonstrated. Additionally, a thermally assisted domain writing scheme is implemented, allowing the preparation of Mn3Sn into a defined antiferromagnetic domain state.