Elastic and anelastic relaxations associated with the incommensurate structure of Pr_{0.48}Ca_{0.52}MnO_{3}

Carpenter, Michael and Howard, Christopher and McKnight, Ruth and Migliori, Albert and Betts, Jon and Fanelli, Victor (2010) Elastic and anelastic relaxations associated with the incommensurate structure of Pr_{0.48}Ca_{0.52}MnO_{3}. Physical Review B, 82 (13). ISSN 1098-0121 DOI 10.1103/PhysRevB.82.134123

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Official URL: http://dx.doi.org/10.1103/PhysRevB.82.134123

Abstract

The elastic and anelastic properties of a polycrystalline sample of Pr0.48Ca0.52MnO3 have been investigated by resonant ultrasound spectroscopy, as a function of temperature (10–1130 K) and magnetic field strength (0–15 T). Marked softening of the shear modulus as the Pnma↔incommensurate phase transition at ∼235 K in zero field is approached from either side is consistent with pseudoproper ferroelastic character, driven by an order parameter with Γ3+ symmetry associated with Jahn-Teller ordering. This is accompanied by an increase in attenuation just below the transition point. The attenuation remains relatively high down to ∼80 K, where there is a distinct Debye peak. It is attributed to coupling of shear strain with the Γ3+ order parameter which, in turn, controls the repeat distance of the incommensurate structure. Kinetic data extracted from the Debye peak suggest that the rate-controlling process could be related to migration of polarons. Elastic softening and stiffening as a function of magnetic field at constant temperatures between 177 and ∼225 K closely resembles the behavior as a function of temperature at 0, 5, and 10 T and is consistent with thermodynamically continuous behavior for the phase transition in both cases. This overall pattern can be rationalized in terms of linear/quadratic coupling between the Γ3+ order parameter and an order parameter with Σ1 or Σ2 symmetry. It is also consistent with a dominant role for spontaneous strains in determining the strength of coupling, evolution of the incommensurate microstructure, and equilibrium evolution of the Jahn-Teller ordered structure through multicomponent order-parameter space.

Item Type: Article
Uncontrolled Keywords: 2010AREP; IA61;
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
Journal or Publication Title: Physical Review B
Volume: 82
Identification Number: 10.1103/PhysRevB.82.134123
Depositing User: Sarah Humbert
Date Deposited: 26 Nov 2010 17:45
Last Modified: 23 Jul 2013 10:00
URI: http://eprints.esc.cam.ac.uk/id/eprint/1970

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