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| - Short- and Long-Range Orbital Order in Phase Separated Pr0.50Ca0.50Mn0.99Ti0.01O3: Its Role in Thermal Hysteresis
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| - By means of high resolution synchrotron X-ray and neutron powder diffraction we have investigated the structural evolution of Pr0.50Ca0.50Mn0.99Ti0.01O3. We have found two structural transitions on cooling; the first takes place at TCO ≃ 240 K and the second in a wide temperature range around 100−140 K. Below the first transition two phases coexist; one presents robust charge/orbital ordering, characterized by strong lattice distortions and low strain, and the second presents charge/orbital order characterized by smaller lattice distortions with remarkable spatial fluctuations and short ranged orbital ordering. This second phase is metastable giving rise to thermal hysteresis of structural and macroscopic properties in the cooling−heating cycle. We have observed that thermal hysteresis is due to (i) the transformation of a huge region of short-ranged order into long-ranged ordered regions and (ii) a hardening of the remaining short-ranged regions in which the lattice distortion grows and the strain diminishes. We also report a detailed characterization of the low temperature (ground state) coexisting phases including their structural details, ordered magnetic structures, coherence lengths, microstructural details, and so forth. A great degree of magnetic disorder characterizes the low temperature ground state of the investigated highly diluted manganite.
- Coexistence of two phases showing short and long-range orbital order have been found in phase separated Pr0.50Ca0.50Mn0.99Ti0.01O3. This coexistence is highly hysteretical under a cooling heating cicle. This phenomenon drives this system and other lowly substituted manganites to display thermal hysteresis of macroscopic properties like magnetization or electric resistance.
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| Alternative Title
| - Orbital Order in Pr0.50Ca0.50Mn0.99Ti0.01O3
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