Effects of vacancy concentration on the magnetic and transport properties of (La1−xPbx)1−y□yMnO3 |
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Authors: | Guerman Popov |
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Institution: | Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 610 Taylor Road, Piscataway, NJ 08854-8087, USA |
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Abstract: | (La1−xPbx)1−y□yMnO3 with x=0.05-0.5 and y=0, 0.05, 0.1 (where □ is a vacancy) was studied to evaluate the effects of A-site vacancies on the physical properties. In this system manganese perovskites form with tolerance factors close to 1 and low A-site cation size mismatch due to similarities in the effective ionic radii of La3+ and Pb2+. Increasing vacancy concentration indicates no significant effect on the lattice parameters or volume. However, the vacancies introduce a greater A-site cation size mismatch, which leads to a lowering of the ferromagnetic and metal-insulator transition temperatures, although the transitions are not broadened with increasing vacancy content. Due to the vacancies a distribution of Mn-O-Mn angles and Mn-O distances are created, and long range order in (La1−xPbx)1−y□yMnO3 appears to be determined by Mn-O-Mn angles and Mn-O distances which most distort from 180° and are the longest, respectively, in the structure. |
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