Using perturbed-angular-correlation (PAC) spectroscopy, via the Hf-->Ta probe, we have measured Mn-site electric-field gradients (EFG's) at Ta nuclei in ceramic samples of LaMnO3. Two crystallographic phases coexist over a temperature interval of ≈16 K near the orthorhombic-to-rhombohedral transition at ≈724 K, which shows a thermal hysteresis of ≈1.7±0.2 K. Concurrently, in the two phases, we determined the temperature dependence of the EFG parameters, Vzz, ƞ, and δ, and the ratio of the probe concentrations A1/A2. To explain the apparent coexistence of two phases in this weakly first-order transition, we present a model that assumes a spatial distribution of Tc values. This distribution could arise from a spatially nonuniform distribution of Mn^4+ ions. We show the PAC technique to be uniquely powerful probe of local symmetries that reflect the effects of a local distribution of valences, which drive the phase transition.
Original Publication Citation
Gary L. Catchen, William E. Evenson and David Allred, "Structural phase transition and Tc distribution in Hf-doped LaMnO3 investigated using perturbed-angular-correlation spectroscopy," Phys. Rev. B 54(6), 3679-82 (1996). [http://link.aps.org/doi/1.113/PhysRevB.54.R3679][1.113/PhysRevB.54.R3679].
BYU ScholarsArchive Citation
Evenson, William E.; Allred, David D.; and Catchen, Gary L., "Structural Phase Transition and Tc Distribution in Hf-doped LaMnO3 Investigated Using Perturbed-Angular-Correlation Spectroscopy" (1996). Faculty Publications. 1152.
American Physical Society
Physical and Mathematical Sciences
Physics and Astronomy
© 1996 American Physical Society (APS)
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