Volume contraction and resistivity drop at the Jahn-Teller transition in La{sub 1-x}Ca{sub x}MnO{sub 3}
Journal Article
·
· Physical Review. B, Condensed Matter and Materials Physics
- Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9 (France)
- School of Engineering, University of Newcastle, University Drive, Callaghan, NSW 2308 (Australia)
- European Synchrotron Radiation Research Facility, BP 220, 38043 Grenoble Cedex (France)
- Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Calcutta 700 064 (India)
We have investigated the Jahn-Teller transition accompanied by orbital order-disorder transition in La{sub 1-x}Ca{sub x}MnO{sub 3} by high temperature x-ray powder diffraction with synchrotron radiation and resistivity measurements. The unit cell volume of LaMnO{sub 3} decreases with increasing temperature in a narrow temperature range below T{sub JT}{approx_equal}750 K and then undergoes a volume collapse at T{sub JT}. The transition is first order. Similar behavior is also obtained in Ca-doped La{sub 1-x}Ca{sub x}MnO{sub 3} for x=0.025 and 0.075. The amount of volume collapse, however, decreases with the doping and also the first order discontinuous transition crosses over to a quasi-continuous transition with doping. We interpret the volume contraction at the transition is due to a more efficient packing of the MnO{sub 6} octahedra in the orbitally liquid state and the crossover from the discontinuous to the quasi-continuous transition is due to the change in the anharmonic coupling parameter with the hole doping. The resistivity of LaMnO{sub 3} decreases as a function of temperature and then shows abrupt drop at T{sub JT} becoming almost temperature independent at higher temperature. The resistivity of La{sub 1-x}Ca{sub x}MnO{sub 3} also decreases at T{sub JT} but the abrupt drop becomes smeared out at higher doping. The similar behavior of the unit cell volume and the resistivity at the Jahn-Teller transition suggests that the volume contraction at T{sub JT} causes delocalization of e{sub g} electrons.
- OSTI ID:
- 20787965
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 9 Vol. 73; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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