Structural changes, clustering, and photoinduced phase segregation in Pr0.7Ca0.3MnO3

被引:252
作者
Cox, DE [1 ]
Radaelli, PG
Marezio, M
Cheong, SW
机构
[1] Brookhaven Natl Lab, Dept Phys, Upton, NY 11973 USA
[2] Inst Max Von Laue Paul Langevin, F-38042 Grenoble 09, France
[3] CNR, MASPEC, I-43100 Parma, Italy
[4] AT&T Bell Labs, Lucent Technol, Murray Hill, NJ 07974 USA
[5] Rutgers State Univ, Dept Phys & Astron, Piscataway, NJ 08855 USA
关键词
D O I
10.1103/PhysRevB.57.3305
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
The structural properties of Pr0.7Ca0.3MnO3 were studied by x-ray synchrotron and neutron-powder diffraction as a function of temperature (15 < T < 300 K), and as a function of x-ray fluence at 15 and 20 K. The temperature evolution of the lattice parameters and of the superlattice reflections is consistent with the development of charge and orbital ordering below T-CO similar to 180 K, followed by antiferromagnetic ordering below T-N similar to 140 K, similar to what was previously observed for La0.5Ca0.5MnO3. Below T-C similar to 120 K, the magnetic structure develops a ferromagnetic component along the a axis on the Mn ions. At low temperatures, a small ferromagnetic moment of 0.45(2)mu(B), oriented in the same direction appears on the Pr ions as well. The observation in Pr0.7Ca0.3MnO3 of significant lattice strain developing below T-CO, as well as the development of a ferromagnetic component to the magnetic structure at T-C similar to 120 K, can be interpreted in terms of the presence of ferromagnetic clusters with an associated lattice distortion from the average structure. At low temperatures, exposure to the x-ray beam produces a phase-segregation phenomenon, whereby the ferromagnetic droplets coalesce into larger aggregates. Further exposure results in a gradual melting of the charge-ordered phase and the formation of a second phase, recently shown to be a ferromagnetic metallic phase by Kiryukhin et al. [Nature (London) 386, 813 (1997)]. The ferromagnetic phase has a significantly smaller a lattice parameter and unit-cell volume (Delta V/V similar to 0.4%) than that of the charge-ordered phase.
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页码:3305 / 3314
页数:10
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