Structural, magnetic and magnetotransport behavior of La0.7SrxCa0.3−xMnO3 compounds |
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Authors: | TD ThanhLH Nguyen DH ManhNV Chien PT Phong NV KhiemLV Hong NX Phuc |
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Institution: | a Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay District, Ha Noi, Viet Nam b Nha Trang Pedagogic College, Nguyen Chanh Street, Nha Trang City, Khanh Hoa Province, Viet Nam c Hong Duc University, 307 Le Lai Street, Thanh Hoa City, Viet Nam |
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Abstract: | A systematic investigation of the structural, magnetic and electrical properties of a series of nanocrystalline La0.7SrxCa0.3−xMnO3 materials, prepared by high energy ball milling method and then annealed at 900 °C has been undertaken. The analysis of the XRD data using the Win-metric software shows an increase in the unit cell volume with increasing Sr ion concentration. The La0.7SrxCa0.3−xMnO3 compounds undergo a structural orthorhombic-to-monoclinic transition at x=0.15. Electric and magnetic measurements show that both the Curie temperature and the insulator-to-metal transition temperature increase from 259 K and 253 K correspondingly for La0.7Ca0.3MnO3 (x=0) to 353 K and 282 K, respectively, for La0.7Sr0.3MnO3 (x=0.3). It is argued that the larger radius of Sr2+ ion than that of Ca2+ is the reason to strengthen the double-exchange interaction and to give rise to the observed increase of transition temperatures. Using the phenomenological equation for conductivity under a percolation approach, which depends on the phase segregation of ferromagnetic metallic clusters and paramagnetic insulating regions, we fitted the resistivity versus temperature data measured in the range of 50-320 K and found that the activation barrier decreased with the raising Sr2+ ion concentration. |
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Keywords: | Manganite Electron-electron scattering Metal-insulator transitions Phase segregation Nanoparticle Resistivity |
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