Journal article
Damping and softening of transverse acoustic phonons in colossal magnetoresistive La0.7Ca0.3MnO3 and La0.7Sr0.3MnO3
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PHYSICAL REVIEW B
Publication Details
Journal: Physical Review B
Author list: Helton JS, Zhao Y, Shulyatev DA, Lynn JW
Publisher: American Physical Society
Place: COLLEGE PK
Publication year: 2019
Journal: Physical Review B
Volume number: 99
Issue number: 2
ISSN: 2469-9950
eISSN: 2469-9969
View additional information: View in Web of Science™

Abstract
Neutron spectroscopy is used to probe transverse acoustic phonons near the (2, 2, 0) Bragg position in colossal magnetoresistive La0.7Ca0.3MnO3 and La0.7Sr0.3MnO3. Upon warming to temperatures near T-c = 257 K the phonon peaks in La0.7Ca0.3MnO3 soften and damp significantly with the phonon half width at half maximum approaching 2.5 meV for phonons at a reduced wave vector of (q) over right arrow = (0.2, 0.2, 0). Concurrently a quasielastic component develops that dominates the spectrum near the polaron position at high temperatures. This quasielastic scattering is approximate to 5 times more intense near T-c than in La0.7Sr0.3MnO3 despite comparable structural distortions in the two. The damping becomes more significant near the polaron position with a temperature dependence similar to that of polaron structural distortions. An applied magnetic field of 9.5 T only partially reverses the damping and quasielastic component, despite smaller fields being sufficient to drive the colossal magnetoresistive effect. The phonon energy, on the other hand, is unaffected by field. The damping in La0.7Sr0.3MnO3 near T-c at a reduced wave vector of (q) over right arrow = (0.25, 0.25, 0) is significantly smaller but displays a similar trend with an applied magnetic field.

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Last updated on 2020-01-07 at 00:10