Devido aos problemas de deficiência de Mn relatados em soja Roundup Ready, à tendência de aumento de cultivo da soja Intacta RR2 PRO® no Brasil e à possibilidade de aumento de rendimentos desta soja relacionado à resposta a adubação foliar com Mn, realizou-se o presente trabalho. Este foi dividido em dois estudos em casa de vegetação (estudos I e II) e um em campo (estudo III). Cada estudo foi realizado em dois solos (um com alto teor de Mn e outro com baixo teor de Mn), avaliando-se os resultados de cada um separadamente. Estudo I: Dois experimentos foram realizados em delineamento em blocos aleatorizados, com quatro repetições e em esquema fatorial 2 × 6 × 4 com parcela subdividida no tempo. Formaram-se 48 tratamentos pela combinação de dois níveis do fator soja (cultivada sem ou com glifosato) e seis do fator fonte do nutriente (sem Mn ou Controle, Cloreto, Sulfato, Carbonato, EDTA e Citrato) alocados nas parcelas principais, e de quatro níveis do fator tempo (4, 24, 48 e 72 h após a aplicação do fertilizante) alocados nas subparcelas. Cada tratamento foi aplicado com uma haste flexível de algodão nas folhas e nos três primeiros trifólios (trifólios tratados) da planta de soja em estádio V4. Avaliou-se a absorção foliar de Mn através da determinação de massa de matéria seca, teor e conteúdo de Mn dos trifólios tratados e da haste de plantas de soja ainda em estádio V4. Estudo II: Dois experimentos foram realizados em delineamento em blocos aleatorizados, com quatro repetições e em esquema fatorial 2 × 6. Formaram-se 12 tratamentos pela combinação de dois níveis do fator soja e seis níveis do fator fonte do nutriente. Cada tratamento foi aplicado nos trifólios tratados da planta de soja em estádio V4. Avaliou-se a distribuição foliar de Mn através da determinação de massa de matéria seca, teor e conteúdo de Mn dos trifólios tratados, hastes, trifólios formados após a aplicação dos tratamentos (trifólios não tratados), vagens e grãos de plantas de soja em estádio R8. Estudo III: Realizaram-se dois experimentos em delineamento similar ao do estudo II, mas com seis blocos. Cada tratamento foi aplicado com pulverizador de pressão constante sobre a parte aérea de plantas de soja em estádio V4. Avaliou-se a massa de matéria seca, teor e conteúdo de Mn das hastes, vagens e grãos de plantas de soja em estádio R8. Foram avaliados também componentes de produção e rendimento de grãos. A quantidade absorvida de Mn é dependente da fonte utilizada e a fonte Cloreto foi a que proporcionou maior absorção de Mn, enquanto a fonte EDTA, apresentou maior eficiência em aumentar o conteúdo de Mn das hastes logo após a aplicação. O Mn aplicado nos trifólios pode ser redistribuído desta parte para outras da planta, embora aparentemente em pequenas quantidades, e até o final do ciclo da soja estará em maior proporção nos trifólios tratados. A soja tratada com Mn não apresentou grãos com maior acúmulo deste, mas na soja cultivada no \"solo -Mn\" e sem glifosato o conteúdo de Mn foi maior do que na soja com glifosato. Em termos de produtividade de grãos, a adubação foliar com Mn em aplicação única na soja no estádio V4 recebendo ou não aplicação de glifosato e cultivada em solo originalmente com alto teor de Mn não proporcionou diferenças. / Due to Mn deficiency problems related to Roundup Ready soybean, the tendency to increase cultivation of Intacta RR2 PROTM soybeans in Brazil and to the possibility of increased yield of this related to the response to Mn foliar fertilization, this work was carried out. It was divided into two greenhouse studies (I and II) and one in the field (study III). Each study was performed in two soils (one with high content of Mn and the other with low content), evaluating the results of each one separately. Study I: the two trials carried out by using factorial split-plot design, with three factors in four replications in randomized complete block design (RCBD). Soybean factor with two levels (without and with glyphosate) and Mn source factor with six levels (Control, Chloride, Sulphate, Carbonate, EDTA and Citrate), both distributed in factorial form into main plots and time factor (4, 24, 48 and 72 h after fertilizer application) distributed in the sub-plots. Each treatment was applied with a swab in the unifoliate leaves and the first three trifoliates (treated trifoliates) of soybean in V4 stage. Mn foliar absorption was determined by dry matter mass, concentration and content of Mn of treated trifoliates and stem of soybean plants in the V4 stage. Study II: The two trials carried out by using 2 × 6 factorial with four replications in RCBD. Soybean factor with two levels and Mn fertilizer source factor with six levels. Each treatment was applied to the treated trifoliates of the V4 soybean plant. the leaf distribution of Mn was determined by the dry matter mass, concentration and Mn content of the treated trifoliates, stems, trifoliates formed after the application of the treatments (untreated trifoliates), pods and grains of soybean plants in the R8 stage. Study III: Two experiments were carried out in a similar design of study II, but with six replications. Each treatment was applied with a constant pressure sprayer on the above ground part of V4 soybean plants. The foliar Mn was evaluated by determining the dry matter mass, content and Mn content of the stems, pods and grains of soybean plants at stage R8. Production components and grain yield were also evaluated. The absorbed amount of Mn is dependent on the source used and the Chloride is the one that provided the highest Mn absorption, but sources such as EDTA showed a higher efficiency in increasing the Mn content of the stems soon after application. The Mn applied in the trifoliates can be redistributed from this part to others of the plant, although apparently in small amounts, and will be in greater proportion in the treated trifoliates until the end of the soybean cycle. Mn-treated soybean did not present grains with higher accumulation, but in soybean cultivated grown in soil with low Mn concentration and without glyphosate the Mn content was higher than in soybean with glyphosate. In terms of grain yield, the foliar fertilization with Mn in single application in the soybean V4 stage without or with glyphosate grown in soil with high Mn content did not present significant differences.

Abstract Aluminum oxide was utilized as a carrier of active metals copper and manganese. Catalysts with various metal ratios and weight loadings were produced by incipient impregnation to treattoluene. From the 24 catalysts we prepared, this investigation selected the most effective catalyst, based on the conversion rate of toluene and CO2 yield. The influence of operating parameters of toluene oxidization on the conversion rate and long-term variations in catalytic activity were investigated, and the physical properties of catalysts were determined by SEM and XRD. The conversion rate for toluene and CO2 yield reached 95% when the Cu/Mn catalyst was used with a metal ratio of 1:1 and 20% loading at 350¢XC, an influent toluene concentration of 1000ppm, oxygen concentration of 21%, a space velocity of 12000 hr-1, and relative humidity of 26%. The toluene conversion rate increased as reaction temperature and influent concentration of oxygen increased, but decreased as the initial toluene concentration and space velocity increased. The long-term test proceeded for seven days at a constant influent toluene concentration of 1000ppm, constant oxygen concentration of 21%, constant space velocity of 12000hr-1 and constant relative humidity of 26%. The stability of the Cu/Mn catalyst structure was assessed. Differences between fresh and aged catalysts were analyzed using analytical instruments such as SEM, and XRD. No obvious deactivation of the catalytic surface was detected. Keywords aluminum oxide, Cu/Mn catalyst, toluene, and operational parameters

Cataract disease affects millions of people worldwide. It is characterized by the accumulation of light-scattering bodies within the lens that reduce visual acuity. Cataracts are effectively treated surgically, but at great expense, costing Medicare $3.4 billion in 1997. Development of an alternative therapy for this disease would provide medical and economic benefits. We have investigated a novel antioxidant, the superoxide scavenger Mn(III)-salophen, as a therapeutic agent in the selenite cataract model. Mn(III)-salophen has been shown to protect E. coli colonies against oxidative stress but was untested in a eukaryotic system. A total dose of 300 mmol/kg, given IP in four equal 75 mmol/kg doses spaced four hours apart, protects 75% of neonatal rats from nuclear cataract development five days after selenite injection. Selenite is toxic through its reaction with the endogenous antioxidant glutathione (GSH). The reduction of selenite to selenide through an intermediate, selenodiglutathione (GSSeSG) leads to generation of superoxide radical, one of several toxic oxygen species that can damage the lens. Mn(III)-salophen causes an in vitro preservation of the lifetime of GSSeSG by interrupting the reduction of selenite. We have established that the reduction of GSSeSG to selenide does not use GSH as a reducing agent, but rather depends upon electrons generated in the earlier reduction of selenite to selenodiglutathione. These electrons can be intercepted by known one-electron scavengers, arresting the metabolism of GSSeSG. Extensive proteolysis of lens crystallins and loss of calcium homeostasis occur in cataractous lenses from a rat treated with sodium selenite. The visual protection with Mn(III)-salophen is accompanied by a partial loss of the calcium homeostasis, a net increase in sodium, and calpain-mediated proteolysis of à -crystallins similar to lenses from animals treated with selenite alone. Although preservation of alpha-crystallins may contribute to the greater transparency in the protected lens, generalized à -crystallin proteolysis is insufficient for cataract formation. From these experiments we propose that Mn(III)-salophen minimizes the oxidative stress imposed upon the cell by interfering with the metabolism of selenodiglutathione. This allows the cell to compensate for the loss of cation homeostasis and prevents aggregation of proteolyzed crystallins into cataracts. / Ph. D.

The aim of this thesis is to determine the level of manganese content and its seasonal dynamics in selected herbs and trees species and invertebrates in the period 2011--2013. Trial sites were located in the highly manganese contaminated ecosystem in Krušné hory mountains. The flora and fauna samples were being collected on a monthly basis. The level of manganese was determined by the AAS method. The highest level of manganese was found in the blackberry bush (Rubus caesius L.) and the raspberry bush (Rubus idaeus L.). The larch (Larix decidua Mill.) and the mountain ash (Sorbus aucuparia L.) were the most contaminated tree species. Majority of plants accumulates manganese during the vegetative period. The invertebrates showed lower level of manganese content than plants. The highest level was found in millipedes (Diplopoda) and isopods (Oniscoidea). Despite the really high concentration of manganese in the enviroment, none of the plants and invertebrates showed symptoms of toxicosis.

Made available in DSpace on 2015-03-26T13:53:33Z (GMT). No. of bitstreams: 1 texto completo.pdf: 974383 bytes, checksum: abbb0708b4390948945a3e2cffed6d90 (MD5) Previous issue date: 2013-07-31 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The Shoot Dieback of Eucalyptus in Vale do Rio Doce (Seca de Ponteiros do Eucalipto do Vale do Rio Doce - SPEVRD) is a physiological disorder which affects eucalyptus plantations in several regions of Brazil, whose causes are still not fully understood. The symptoms of this disorder occur in the transition from the rain season to the dry season, with higher incidence in areas with poor drainage and higher water table when preceded by an intense rainy season. In addition, the accumulation of Mn also seems to be related to SPEVRD, observing higher levels of this nutrient in plant leaves with symptoms. Thus, this proposal was aimed at understanding the possible initial causes of SPEVRD as well as identify possible physiological, enzymatic and, or, fermentation mechanisms that confer greater tolerance of Eucalyptus clone 2719 to this anomaly in relation to sensitive clone hybrid urograndis 1213. A hydroponic experiment was conducted with a factorial 2 x 2 x 2 with two clones (2719 and 1213), two concentrations of O2 (8 e 4 mg L-1) and two Mn (1,39 e 300 mg L-1) using three replicates in randomized block design. Seedlings around 40 day old were maintained in Clark nutrient solution for 30 days and then treatments were applied for 11 days. At the end, it was evaluated gas exchange rate and leaves and roots were collected. The hypoxia affected both clones reducing root dry matter production, but only the tolerant clone suspended leaf growth, keeping the proportion between leaves and roots similar regardless the treatment, while the sensitive clone had an increase in this ratio due to the decrease production of roots and maintenance of leaf growth. The sensitive clone had higher concentrations of Mn in young leaves compared to the tolerant one. In both clones, the photosynthesis rate and stomatal conductance were reduced by hypoxia, but the internal carbon concentration remained high, indicating biochemical limitations to photosynthesis. Due to the maintenance of chlorophyll contents, cellular damage can occur if the absorbed energy is not properly dissipated. These damages were proven by higher levels of malondialdehyde (MDA) in sensitive clone leaves, which increase was not observed in tolerant leaves. In leaves, although the superoxide dismutase (SOD) activity was higher in tolerant clone, both catalase activity and total antioxidant capacity were similar between clones, indicating that the tolerant clone probably has preventive mechanisms to avoid damage caused by reactive oxygen species (ROS) and not only detoxifing them. In roots, MDA levels were also higher in sensitive clone, especially in the treatment with excess of Mn. The tolerant one had a higher SOD activity and increased antioxidant capacity in roots. The activity of alcohol dehydrogenase (ADH), alanine transaminase (AlaT) and aspartate transaminase (AspT) were increased under hypoxia, with the highest elevation of ADH in the sensitive clone which demonstrates to have an increased metabolism, which explains, at least partially, the greater damage. The tolerant clone activates characteristic responses of quiescence, resulting in greater survival of deep roots in hypoxic conditions. Taken together, this response of the tolerant clone to SPEVRD may also increase tolerance to drought, avoiding damage and nutritional disorders that can lead to appearance of symptoms of SPEVRD. On the other hand, the sensitive clone has escape responses to hypoxia, which can confer increased susceptibility to drought, as well as to excess of Mn in leaves and potential damage that can initiate processes which cause this anomaly. / A Seca de Ponteiros do Eucalipto do Vale do Rio Doce (SPEVRD) é uma anomalia que afeta cultivos de eucalipto em várias regiões do Brasil, cujas causas ainda não são completamente entendidas. Os sintomas deste distúrbio ocorrem na época de transição do período chuvoso para o seco, em maior incidência em áreas com drenagem deficiente e elevação do lençol freático quando precedidos por uma intensa época chuvosa. Em adição, o acúmulo de Mn também parece estar relacionado à SPEVRD, observando-se teores mais elevados deste nutriente nas folhas das plantas com sintomas. Assim, a presente proposta teve como objetivo compreender as possíveis causas iniciais da SPEVRD bem como identificar possíveis mecanismos fisiológicos, enzimáticos e, ou, fermentativos de tolerância superior do clone de Eucalyptus 2719 a esta anomalia, em relação ao clone sensível híbrido de urograndis 1213. Foi conduzido um experimento em hidroponia, em esquema fatorial 2 x 2 x 2 com dois clones (2719 e 1213), duas concentrações de O2 (8 e 4 mg L-1) e duas de Mn (1,39 e 300 mg L-1), utilizando-se três repetições em delineamento em blocos casualisados. Foram utilizadas mudas com aproximadamente 40 dias de idade mantidas em solução nutritiva de Clark por mais 30 dias e em seguida foram aplicados os tratamentos por 11 dias. Ao final, avaliaram-se as trocas gasosas das plantas e amostras de folhas e raízes foram coletadas. Ambos os clones tiveram reduções na produção de matéria seca de raízes por efeito da hipóxia, mas apenas o tolerante (2719) suspendeu o crescimento das folhas, mantendo a proporção entre folhas e raízes semelhante independente do tratamento, enquanto o sensível (1213) teve um aumento dessa relação devido à queda de produção de raízes e manutenção do crescimento aéreo. O clone sensível acumulou mais Mn nas folhas novas em relação ao clone tolerante. Em ambos os clones, a taxa fotossintética e a condutância estomática foram reduzidas pela hipóxia, sendo que a concentração interna de carbono manteve-se alta, indicativo de limitações bioquímicas à fotossíntese. Em função da manutenção dos teores de clorofilas danos celulares podem acontecer caso a energia absorvida não seja dissipada corretamente. Estes danos foram comprovados pela elevação dos teores de malonaldeído (MDA) nas folhas do clone sensível, fato não observado no tolerante. Em folhas, embora a atividade da superóxido dismutase (SOD) tenha sido superior no clone tolerante, tanto a atividade da catalase quanto a capacidade antioxidante total foram similares entre os clones, evidenciando que o clone tolerante provavelmente evita os danos por mecanismos preventivos à formação das espécies reativas de oxigênio (ERO) e não apenas desintoxicando-as. Nas raízes, os teores de MDA foram também superiores no clone sensível, especialmente no tratamento com excesso de Mn. O clone tolerante teve uma maior atividade da SOD e maior capacidade antioxidante nas raízes. As atividades da álcool desidrogenase (ADH), da alanina transaminase (AlaT) e da aspartato transaminase (AspT) elevaram-se sob hipóxia, com maior elevação da ADH no clone sensível, que demostra possuir um metabolismo mais intenso, o que explica ao menos parcialmente, os maiores danos. O clone tolerante ativa respostas características de quiescência, traduzindo-se em maior sobrevivência de raízes profundas em condições de hipóxia. Tomados em conjunto, essa resposta deve conferir ao clone tolerante à SPEVRD maior tolerância também ao déficit hídrico, evitando danos e desordens nutricionais que podem levar ao surgimento dos sintomas da SPEVRD. Por outro lado, o clone sensível possui respostas de escape à hipóxia, que em campo podem lhe conferir maior susceptibilidade ao déficit hídrico, como também ao excesso de Mn nas folhas e iniciar possíveis danos e processos que provoquem esta anomalia.

Récemment, notre laboratoire a démontré pour la première fois, que la protéine Damaged DNA Binding 2 (DDB2) possédait une activité régulatrice négative de l’expression basale de la superoxyde dismutase mitochondriale (SOD Mn) en se fixant sur un élément de réponse dans la région promotrice de son gène. Cette protéine était connue jusque là pour sa participation dans le système de réparation de l’ADN par excision de nucléotides. L’objectif de ce travail a été de définir précisément l’implication de ces deux protéines dans la croissance des cellules d’adénocarcinome mammaire, en développant des modèles cellulaires dont l’expression de la SOD Mn ou de la DDB2 est modulée expérimentalement. Nos résultats montrent pour la 1ère fois, que la SOD Mn est surexprimée dans les cellules tumorales mammaires insensibles aux oestrogènes (ER-) et ayant un pouvoir métastatique, et non dans les cellules épithéliales mammaires normales et les cellules ER+. L’inhibition de l’expression de la SOD Mn entraîne une stimulation de la croissance et une diminution de l’invasivité cellulaires, associées à une activité réduite de la métalloprotéinase 9. L’addition d’antioxydants, éliminant spécifiquement l’H2O2 issu de l’activité élevée de la SOD Mn, entraîne à la fois une inhibition de la croissance et du pouvoir invasif des cellules ER-. Ces résultats révèlent que la SOD Mn participe aux capacités invasives des cellules ER- via la production d’H2O2. Nous avons également montré pour la 1ère fois, que la DDB2 présente une activité oncogénique dans les cellules tumorales mammaires sensibles aux oestrogènes (ER+), non seulement parce que son gène est surexprimé, mais également parce qu’elle active leur prolifération en agissant sur la phase de transition G1/S et sur la progression dans la phase S du cycle cellulaire. Contrairement à la SOD Mn, l’expression de la DDB2 n’est pas observée dans les cellules tumorales mammaires ER-. De même à partir de biopsies provenant de patientes atteintes d’un cancer du sein, nous avons montré que la DDB2 est significativement plus exprimée dans les tumeurs les moins agressives et exprimant le récepteur aux oestrogènes. En montrant l’importance de la SOD Mn et la DDB2 dans la croissance et l’invasion des cellules tumorales mammaires, l’ensemble de ce travail révèle ainsi ces deux protéines comme des marqueurs prédictifs potentiels de la progression tumorale, et ouvre de nombreuses perspectives en cancérologie mammaire. / Recently, our laboratory demonstrated for the first time, that Damaged DNA Binding 2 (DDB2) played a role as a negative transcriptional regulator on the mitochondrial superoxide dismutase (MnSOD) expression through its binding to a specific DNA sequence located into the promoter of MnSOD gene. DDB2 was known as a protein which participates in the nucleotide excision repair of DNA. The goal of this study was to define precisely the involvement of the both proteins in the growth of mammary adenocarcinoma cells, using experimental procedures to modulate their expression in the breast cancer cell lines. Our results show for the first time that MnSOD is overexpressed in the estrogen receptor (ER) negative and metastatic breast tumor cells, but not in normal epithelial mammary cells and ER-positive tumor cells. Inhibition of MnSOD expression stimulates proliferation but decreases the invasive ability and the metalloproteinase 9 activity of tumor cells. Elimination of H2O2 from the elevated MnSOD activity by addition of specific antioxidants decreases proliferation as well as invasive ability of tumor cells, suggesting that the role of MnSOD in the invasive ability of tumor cells is mediated by H2O2. We have shown too for the first time that DDB2 has an oncogenic activity in the ER-positive breast tumor cells, because its gene is overexpressed and stimulates the proliferation by activating the entry of cells in the G1/S transition phase and the S phase progression. In contrast to MnSOD, DDB2 expression is not observed in ER-negative breast tumor cells, but is higher in ER-positive than in ER-negative tumor samples from patients with breast carcinoma. Taken together, our findings demonstrate that both MnSOD and DDB2 play a role in the growth and invasiveness of tumor cells and may become a promising candidate as a predictive markers in breast cancer. More studies will be need to define molecular mechanism controlling this activity of these both proteins.

Made available in DSpace on 2014-06-12T17:40:06Z (GMT). No. of bitstreams: 2 arquivo7607_1.pdf: 2211073 bytes, checksum: b41804eead923399b6fc86851c635dc3 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2006 / Este trabalho teve por objetivo estudar alguns tratamentos térmicos para se eliminar ou inibir o processo de estabilização da martensita que é um fenômeno indesejado nas aplicações tecnológicas das ligas com memória de forma, provocando importantes alterações nos fenômenos de memória de forma, resultando em importantes modificações nos comportamentos físicosmecânicos do material. A estabilização da martensita pode ser eliminada ou atenuada através do emprego de tratamentos térmicos específicos ou a utilização de novos elementos de ligas. O estudo do envelhecimento envolve também os comportamentos das interfaces martensita/martensita e austenita/martensita, e da tensão crítica de indução da transformação. Foi estudada uma liga de composição nominal Cu-10%Al-8,4%Mn, que tem temperaturas críticas das transformações martensíticas em torno da temperatura ambiente, obtida a partir da fusão dos elementos químicos num forno de indução de 24 KVa. Amostras foram preparadas para estudo da microestrutura (microscopia ótica), da estrutura cristalina (difração de raios-X), para caracterização das temperaturas de transformação de fase (resistividade elétrica e ensaio de flexão). As amostras foram submetidas aos seguintes tratamentos térmicos de betatização: Têmpera em água a 25°C (BT25), Têmpera em água a 100°C (BT100) e Têmpera ao Ar (BTAr). Em seguida a liga foi caracterizada microestruturalmente apresentando a fase martensítica β 1, que após aquecimento apresenta as características da transformação martensítica inversa, com a fase austenítica ou matriz com estrutura de super-rede DO3. Na difração de raios-X foram obtidas características da fase martensítica β 1, com planos característicos da estrutura ordenada ortorrômbica 18R (β 1). Na resistividade elétrica a baixa temperatura analisou-se o comportamento das curvas de resistividade elétrica versus temperatura, para os diferentes procedimentos de tratamentos térmicos, e a partir das curvas foram determinadas às temperaturas críticas de transformação (AS, AF, MS e MF), as amplitudes térmicas (AT) e as histereses térmicas (HT). Foram realizados ensaios de flexão do tipo viga engastada para simular o efeito memória de forma com uma carga de 13 MPa aplicada à amostra através de um sistema de polia sendo realizada a ciclagem térmica. As curvas da deformação versus temperatura após carregamento da amostra na fase martensítica apresenta uma deformação, em seguida é aquecida e depois resfriada. No aquecimento há um comportamento linear da deformação em função da temperatura. No resfriamento a amostra apresenta um aumento da deformação pseudoplástica. Na resistividade elétrica a alta temperatura verificou-se as modificações nas curvas de temperaturas elevadas onde ocorrem às reações de transição ordem-desordem e de precipitação de fases. Difrações de raios-X foram realizadas a fim de se observar as modificações estruturais da fase martensítica. Os resultados foram analisados em função dos fenômenos da estabilização martensítica tais como supersaturação de lacunas de têmpera e transições ordem-desordem. Os resultados indicam alguns parâmetros que devem ser utilizados para minimizar os problemas causados pelo envelhecimento das ligas Cu-Al-Mn com memória de forma

No description available.

Abstract Recently, the large magneto-resistance effects in epitaxial manganite thin films has interested in the doped manganite perovskite materials for magnetic random access memory (MRAM) and read-head application. The relation between the magneto-resistance and microstructure of the colossal magneto-resistance materials has been evaluated in this study. Different thickness of La0.67Ca0.33Mn03 (LCMO) thin films were grown on (001) MgO and (001) SrTi03 (STO) substrates at growth temperature 750 degree C with RF magnetron sputtering technique, respectively. These substrates provide two different lattice-mismatch conditions for the LCMO films (+9% for MgO and +1% for STO). The crystal structure of LCMO films were characterized with X-ray diffraction (XRD), the surface morphology of LCMO films were observed by scanning electron microscope (SEM), the interface of microstructure between LCMO films and substrate were studied by transmission electron microscope (TEM), the thickness and chemical composition of LCMO films were determined by Rutherford backscattering spectrometer (RBS), and finally the resistance and I-M transition temperature were evaluated at temperature range from 77K to 300K. The results show that the epitaxial LCMO films with a superlattice structure were obtained on STO substrate and polycrystal structure of LCMO films were on MgO substrate due to larger lattice mismatch.. The transition temperature of magneto-resistance of LCMO thin film is quite sensitive with film thickness. The transition temperature increases with film thickness increased. When the film with thickness excess of 2000A, the transition temperature is nearly same as that of LCMO bulk material.. The existed strain and the microstructure of LCMO films are two important factors related with magnetic resistance and electrical properties of LCMO films.

Abstract Recent progress in oxide perovskite thin-film technology has led to the discovery of a large negative magnetoresistance in doped manganate perovskite thin films. These films may have potentials for magnetic random access memory (MRAM) and magnetic sensors. Therefore, the research of magnetoresistance has been attracted a lot of attentions. The magnetoresistance is directly related to the microstructure. In an application point of view, the ulta-thin film may be more appropriate compares with those utilizing with thicker films. In this paper, we report the detail results of electrical property of La0.67Ca0.33MnO3 (LCMO) films related with their microstructure. The La0.67Ca0.33MnO3 (LCMO) films were deposited on (001) STO substrate with RF sputtering technique. The working pressure was maintained at 100m torr and the growth temperature was kept at 750¢J. After growth the films was annealed at 850¢J for 1 hour in a 500 torr O2 annealing environment. The growth time was 3mins.¡B6mins. and 12mins. respectively. The crystal structure of LCMO films were characterized with X-ray diffraction (XRD). The surface morphology of LCMO films were observed by scanning electron microscope (SEM) and the interface of microstructure between LCMO films and STO substrate were investigated by transmission electron microscope (TEM). Finally the M-I transition temperature were evaluated with 4-point probe at the temperature range from 300K down to 77K. The results show that the LCMO films were amorphous when the growth time was in 3 mins. The microstructure of the film gradually became poly-crystal and had a (001) prefer orientation after the growth time increasing to 6 mins. The grain size of the 12 mins growth film was at 40-50 nm scale. The Curie temperature and magnetoresistance change of these films were increased as the degree of crystallization of these films became better.