Acoustic phonon dispersion and diffuse scattering across the valence transition of ${\left(\mathrm{P}{\mathrm{r}}_{0.85}{\mathrm{Y}}_{0.15}\right)}_{0.7}\mathrm{C}{\mathrm{a}}_{0.3}\mathrm{Co}{\mathrm{O}}_{3-\delta }$

Journal Article · 02 August 2019 · Physical Review B

DOI: https://doi.org/10.1103/PhysRevB.100.054101 · OSTI ID:1557613

Phelan, D. ^[1]; Krogstad, M. J. ^[1]; Schreiber, N. J. ^[2]; Osborn, R. ^[1]; Said, A. H. ^[3]; Zheng, H. ^[1]; Rosenkranz, S. ^[1]

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1. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division
2. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division; Cornell Univ., Ithaca, NY (United States)
3. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)

A number of praseodymium-containing cobalt perovskites undergo temperature-dependent metal-insulator transitions that involve a transfer of electrons between cobalt and praseodymium cations. We have used high- resolution inelastic x-ray scattering to directly measure the changes in the acoustic phonon dispersion through this transition in one such single crystal, (Pr_0.85Y_0.15)(0.)7Ca_0.3CoO_3-$$\delta$$, in an effort to understand the role of the lattice in the transition. Transverse and acoustic modes were measured in the pseudocubic (200), (220), and (222) zones both above and below the transition temperature. The resultant dispersion curves reveal that the transition is associated with a significant hardening of the pseudocubic C₁₁ elastic constant, whereas C₁₂ and C₄₄ do not significantly change. Here, analysis of the temperature-dependent damping of the longitudinal acoustic mode in the (200) zone reveals a peak in the damping at temperatures just above the transition temperature. Significant elastic diffuse scattering is also observed above the transition temperature, likely resulting from clusters in which the electron transfer is beginning to occur as a precursor to the phase transition. The presence of these clusters likely limits the phonon lifetimes, thus leading to the observed damping.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1557613
• Journal Information: Physical Review B, Journal Name: Physical Review B Journal Issue: 5 Vol. 100; ISSN 2469-9950; ISSN PRBMDO
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English