Raman study of magnetic excitations and magnetoelastic coupling in $\ensuremath{\alpha}{\text{-SrCr}}_{2}{\text{O}}_{4}$

Raman study of magnetic excitations and magnetoelastic coupling in $α {-SrCr}_{2} O_{4}$

Michael E. Valentine, Seyed Koohpayeh, Martin Mourigal, Tyrel M. McQueen, Collin Broholm, Natalia Drichko, Siân E. Dutton, Robert J. Cava, Turan Birol, Hena Das, and Craig J. Fennie

Phys. Rev. B 91, 144411 – Published 13 April 2015

Abstract

Using Raman spectroscopy, we investigate the lattice phonons, magnetic excitations, and magnetoelastic coupling in the distorted triangular-lattice Heisenberg antiferromagnet $α {-SrCr}_{2} O_{4}$ , which develops helical magnetic order below 43 K. Temperature-dependent phonon spectra are compared to predictions from density functional theory calculations which allows us to assign the observed modes and identify weak effects arising from coupled lattice and magnetic degrees of freedom. Raman scattering associated with two-magnon excitations is observed at 20 and 40 meV. These energies are in general agreement with our ab initio calculations of exchange interactions and earlier theoretical predictions of the two-magnon Raman response of triangular-lattice antiferromagnets. The temperature dependence of the two-magnon excitations indicates that spin correlations persist well above the Néel temperature.

Received 4 April 2014
Revised 22 January 2015

DOI:https://doi.org/10.1103/PhysRevB.91.144411

Authors & Affiliations

Michael E. Valentine, Seyed Koohpayeh, Martin Mourigal^*, Tyrel M. McQueen, Collin Broholm, and Natalia Drichko^†

Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA

Siân E. Dutton^‡ and Robert J. Cava

Institute for Quantum Matter and Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA

Turan Birol⁴

School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA and Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA

Hena Das and Craig J. Fennie

School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA

^*Present Address: School of Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA.
^†Corresponding author: drichko@jhu.edu
^‡Present Address: Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.

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Vol. 91, Iss. 14 — 1 April 2015

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Physical Review B

covering condensed matter and materials physics

Raman study of magnetic excitations and magnetoelastic coupling in $α {-SrCr}_{2} O_{4}$

Michael E. Valentine, Seyed Koohpayeh, Martin Mourigal, Tyrel M. McQueen, Collin Broholm, Natalia Drichko, Siân E. Dutton, Robert J. Cava, Turan Birol, Hena Das, and Craig J. Fennie

Phys. Rev. B 91, 144411 – Published 13 April 2015

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Physical Review B

covering condensed matter and materials physics

Raman study of magnetic excitations and magnetoelastic coupling in α-SrCr2O4

Michael E. Valentine, Seyed Koohpayeh, Martin Mourigal, Tyrel M. McQueen, Collin Broholm, Natalia Drichko, Siân E. Dutton, Robert J. Cava, Turan Birol, Hena Das, and Craig J. Fennie

Phys. Rev. B 91, 144411 – Published 13 April 2015

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Raman study of magnetic excitations and magnetoelastic coupling in $α {-SrCr}_{2} O_{4}$