JahnTeller effect and stability of the chargeordered state in La _{1  x} Ca _{x} MnO_{3} (0.5 <= x <= 0.9) manganites
Abstract
The longitudinal ultrasonic sound velocity and attenuation, the resistivity, and lattice parameters were studied as a function of temperature from 30 K to 300 K in La _{1  x} Ca _{x} MnO_{3} (0.5 <= x <= 0.9). For all the samples, a dramatic stiffening of the sound velocity below the charge ordering transition temperature T_{CO} was directly driven by distinct changes of the lattice parameters due to the formation of longrange ordering of JahnTeller distorted MnO _{6} octahedra. The relative change of the sound velocity (∆V/V) below T_{CO} depends on the Ca concentration x and reaches the maximum at x = 0.75, implying that the effective strength of the electronlattice interaction with the JahnTeller distortion is the strongest at x = 0.75 and hence the chargeordered state is mostly stabilized near x = 0.75 and insensitive to the application of a magnetic field, which is supported by the charge transport properties under high magnetic fields up to 14 T.
 Publication:

EPL (Europhysics Letters)
 Pub Date:
 December 2002
 DOI:
 10.1209/epl/i2002003612
 arXiv:
 arXiv:condmat/0212012
 Bibcode:
 2002EL.....60..670L
 Keywords:

 43.35.+d;
 64.70.Kb;
 71.38.k;
 Ultrasonics quantum acoustics and physical effects of sound;
 Solidsolid transitions;
 Polarons and electronphonon interactions;
 Condensed Matter  Strongly Correlated Electrons
 EPrint:
 16 pages, 5 figures, PDF