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Lattice disorder in strongly correlated lanthanide and actinide intermetallics (2001)

Booth, C. H. ; Bauer, E. D. ; Maple, M. B. ; [et al.]

Chester : International Union of Crystallography (IUCr)

Journal of synchrotron radiation 8 (2001), S. 191-195

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ISSN: 1600-5775

Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001

Topics: Geosciences , Physics

Notes: Lanthanide and actinide intermetallic compounds display a wide range of correlated-electron behavior, including ferromagnetism, antiferromagnetism, nonmagnetic (Kondo) ground states, and so-called `non-Fermi liquid' (NFL) behavior. The interaction between f electrons and the conduction band is a dominant factor in determining the ground state of a given system. However, lattice disorder can create a distribution of interactions, generating unusual physical properties. These properties may include NFL behavior in many materials. In addition, lattice disorder can cause deviations from standard Kondo behavior that is less severe than NFL behavior. A review of the lattice disorder mechanism within a tight-binding model is presented, along with measurements of the YbBCu4 and UPdxCu5−x systems, demonstrating the applicability of the model. These measurements indicate that while the YbBCu4 system appears to be well ordered, both site interchange and continuous bond-length disorder occur in the UPdxCu5−x series. Nevertheless, the measured bond-length disorder in UPdCu4 does not appear to be enough to explain the NFL properties simply with the Kondo disorder model.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1107/S0909049500019026

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Effects of Magnetization on Hole Localization and MnO6 Octahedra Disorder in Hole-Doped Lanthanum Manganese Perovskites (1999)

Booth, C. H. ; Bridges, F. ; Neumeier, J. J. ; [et al.]

Springer

Journal of superconductivity 12 (1999), S. 295-298

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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.