Relationship between structural parameters and the Neel temperature in Sr{sub 1-x}Ca{sub x}MnO{sub 3} (0{<=}x{le}1) and Sr{sub 1-y}Ba{sub y}MnO{sub 3} (y{<=}0.2)
The crystal and magnetic structures of newly synthesized Sr{sub 1-x}Ca{sub x}MnO{sub 3} (0{<=}x{le}1) and Sr{sub 1-y}Ba{sub y}MnO{sub 3} (y{<=}0.2) perovskite materials (of the ABO{sub 3} type) were investigated using neutron and synchrotron x-ray powder diffraction at temperatures between 10 and 530 K. Upon decreasing the size of the A-site ion (or the unit-cell size) a series of structural transitions appears at room temperature from cubic Pm{bar 3}m to tetragonal I4/mcm (at x{approx}0.3) to orthorhombic Pbnm at x{approx}0.4. In agreement with neutron-diffraction data, resistive and magnetic measurements show that the samples are antiferromagnetic with Neel temperatures T{sub N}, varying from 233 to {approx}125 K and from 233 to 212 K by increasing the Ca and Ba contents, respectively. The observed variation of T{sub N} cannot be solely explained by the changes of the unit-cell size or the average Mn-O-Mn bond angle {theta}. The behavior of T{sub N} can be satisfactorily described as a function of <cos{sup 2} {theta}> related to the superexchange interaction integral, and {sigma}{sup 2}, the A-site ionic size variance [L. M. Rodriguez-Martinez and J. P. Attfield, Phys. Rev. B 54, R15 622 (1996)] regardless of the structural symmetry of the perovskite material.
- Sponsoring Organization:
- (US)
- DOE Contract Number:
- W-31-109-ENG-38
- OSTI ID:
- 40277652
- Journal Information:
- Physical Review B, Vol. 64, Issue 13; Other Information: DOI: 10.1103/PhysRevB.64.134412; Othernumber: PRBMDO000064000013134412000001; 012137PRB; PBD: 1 Oct 2001; ISSN 0163-1829
- Publisher:
- The American Physical Society
- Country of Publication:
- United States
- Language:
- English
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