Mingguang Wang
材料科学技术（英文）
Transmission electron microscopy (TEM) and high resolution electron microscopy (HREM) have been used to study the microstructural properties of La0.7Ca0.3MnO3 films on (001) LaAlO3 substrates prepared by direct current magnetron sputtering technique. The as-grown thin films with different thickness are perfectly coherent with the substrates. The film suffers a tetragonal deformation in the area near the interface between the film and the substrate. With increasing thickness, the film is partially relaxed. It was found that La0.7Ca0.3MnO3 films consist of two types of oriented domains described as: (1) (110)f [001]f||(001)s[100]s and (1¹10)f [001]f||(001)s[100]s and (2) (110)f [001]f||(001)s[010]s and (1¹10)f [001]f//(001)s[010]s. Upon annealing, the film is relaxed by the formation of mis¯t dislocations. Other than mis¯t dislocations, two types of threading dislocations with Burgers vector of <100> and <110> were also identified.
关键词:
Colossal magnetoresistance
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Baoxin HUANG
,
Yihua LIU
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Ruzhen ZHANG
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Chengjian WANG
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Gang JI
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Liangmo MEI
材料科学技术（英文）
The Gd substituting effects for La in La0.67Ca0.33MnO3 has been studied. With increasing the substituting amount of Gd, the phase transition temperature of metal-isolator for the samples decreases, the corresponding peak resistivity increases,the Curie temperature decreases monotonically. The substitution of La-Ca-Mn-O with 11% Gd for La improved the magnetoresistance ratio by an order of magnitude. The effects of substituting Gd can be explained in terms of the lattice effects. An irreversible MR behaviour was observed in Gd-substituting compounds. This effect became marked when the substituting amount of Gd was greater than 7%. A maximum irreversible increment of MR ratio as large as 91% was obtained when Gd substituting amount was 11%.
关键词:
Manganese perovskites
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