Strong spin-phonon coupling in infrared and Raman spectra of SrMnO3

Abstract

Infrared reflectivity spectra of cubic SrMnO${}_3$ ceramics reveal 18 % stiffening of the lowest-frequency phonon below the antiferromagnetic phase transition occurring at T${}_N$ = 233 K. Such a large temperature change of the polar phonon frequency is extraordinary and we attribute it to an exceptionally strong spin-phonon coupling in this material. This is consistent with our prediction from first principles calculations. Moreover, polar phonons become Raman active below T${}_N$, although their activation is forbidden by symmetry in $Pm\bar{3}m$ space group. This gives evidence that the cubic $Pm\bar{3}m$ symmetry is locally broken below T${}_N$ due to a strong magnetoelectric coupling. Multiphonon and multimagnon scattering is also observed in Raman spectra. Microwave and THz permittivity is strongly influenced by hopping electronic conductivity, which is caused by small non-stoichiometry of the sample. Thermoelectric measurements show room-temperature concentration of free carriers $n_e=$3.6 10${}^{20}$ cm${}^{-3}$ and the sample composition Sr${}^{2+}$Mn${}_{0.98}^{4+}$Mn${}_{0.02}^{3+}$O${}_{2.99}^{2-}$. The conductivity exhibits very unusual temperature behavior: THz conductivity increases on cooling, while the static conductivity markedly decreases on cooling. We attribute this to different conductivity of the ceramic grains and grain boundaries.

subm. to PRB

References in corpus (4)

• Two-phonon coupling to the antiferromagnetic phase transition in multiferroic BiFeO3
• Large spin-phonon coupling and magnetically-induced phonon anisotropy in Sr$M$O${}_3$ perovskites ($M$=V,Cr,Mn,Fe,Co)
• Optical probe of ferroelectric order in bulk and thin film perovskite titanates
• Universal exchange-driven phonon splitting in antiferromagnets

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• Hexagonal Sr0.6Ba0.4MnO3: Spin and Dipole Coupling via Local Structure
• Magnetic and ferroelectric properties of Sr${}_{1-x}$Ba${}_x$MnO${}_3$ from first principles
• Electronic origin of spin-phonon coupling effect in transition-metal perovskites
• Spin-phonon interaction increased by compressive strain in antiferromagnetic MnO thin films
• Engineering crystal structure and spin-phonon coupling in Ba1-xSrxMnO3