ISSN:
1572-9605
Keywords:
X-ray-absorption fine-structure (XAFS)
;
“colossal” magnetoresistance (CMR)
;
Jahn–Teller polarons
;
La1−x A x MnO3
;
La1−y MnO3+δ
Source:
Springer Online Journal Archives 1860-2000
Topics:
Electrical Engineering, Measurement and Control Technology
,
Physics
Notes:
Abstract We review the distortions of the MnO6 octahedra reduced by magnetization in hole-doped lanthanum manganese perovskites. The systems we consider include the “colossal” magnetoresistance (CMR) samples La1−x Ca x MnO3 (x=0.21, 0.25, 0.30), La0.67Ba0.33MnO3, and a poorer quality La0.67Pb0.33MnO3 sample. We also report preliminary work on three samples of oxygen-doped LaMnO3+δ and a lanthanum-deficient La0.9MnO3 sample. We find the same exponential relationship between the removal of the distortion and the sample magnetization in the Ba- and Pb-doped CMR samples as was found previously for the Ca-doped samples. The MnO6 distortion in the oxygen-doped materials is found to slightly reduce below the magnetic transition, although much less so than in the CMR samples. Above T c, the antiferromagnetic LaMnO3.006 sample shows a softer temperature dependence of the Mn–O bond length distribution broadening. Surprisingly, even this sample shows deviations from thermal (Debye) behavior near T N, possibly due to FM coupling within MnO planes.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1007780727538
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