Probing Spin Correlations with Phonons in the Strongly Frustrated MagnetZnCr2O4

Abstract

The spin-lattice coupling plays an important role in strongly frustrated magnets. In ZnCr2O4, an excellent realization of the Heisenberg antiferromagnet on the pyrochlore network, a lattice distortion relieves the geometrical frustration through a spin-Peierls-like phase transition at T(c)=12.5 K. Conversely, spin correlations strongly influence the elastic properties of a frustrated magnet. By using infrared spectroscopy and published data on magnetic specific heat, we demonstrate that the frequency of an optical phonon triplet in ZnCr2O4 tracks the nearest-neighbor spin correlations above T(c). The splitting of the phonon triplet below T(c) provides a way to measure the spin-Peierls order parameter.

An investigation on magnetism, spin–phonon coupling, and ferroelectricity in multiferroic GdMn2O5

“…For multiferroics RMn 2 O 5 , the high-frequency phonons were ascribed to the Mn-O stretching vibrations which are apt to modulate the Mn-O-Mn superexchange interactions. Therefore, the anomalous phonon shift above T N together with the deviation of the magnetic susceptibility from the C-W law is the outcome of the strong spin-phonon coupling in GdMn 2 O 5 [20], noting that strong spin-phonon coupling has also been observed in other multiferroics RMn 2 O 5 (R = Bi, Eu, and Dy) [18].…”

“…To the firstorder approximation, this dependence can be described by ω = ω 0 + λ S i · S j , where ω 0 is the phonon frequency, and S i · S j is the spatial spin correlation function [20]. For multiferroics RMn 2 O 5 , the high-frequency phonons were ascribed to the Mn-O stretching vibrations which are apt to modulate the Mn-O-Mn superexchange interactions.…”

Far-infrared spectra of the magnetic exchange resonances and optical phonons and their connection to magnetic and dielectric properties of Dy3Fe5OKang1, Standard2, Rogers3 et al. 2012Phys. Rev. B17150View full textAdd to dashboardCite

“…6,7,8,9,10 The microscopic nature of the magnetoelectric effects can be better understood through the studies of the optical excitations such as IR active electromagnons and lattice vibrations that are modified by the spin-lattice interaction. 11,12,13,14,15,16,17,18,19 Due to the coincidence of the temperatures for the FM ordering of Dy spins and the AFE lattice ordering in Dy-IG, we expected an interesting behavior for the low-frequency optical phonons, which are related to the displacements of the heaviest ions (Dy) and spin-related ligand field (LF) transitions and Kaplan-Kittel (KK) 20 magnetic exchange resonance modes in Dy-IG. The main results of this paper are (i) the observed correlation between the magnetic field-induced changes of magnetic susceptibility in Dy-IG is followed by the discussion of the experimental data.…”

Infrared phonon anomaly and magnetic excitations in single-crystal Cu3Bi(SeO3)2OMiller1, Stephens2, Martin3 et al. 2012Phys. Rev. B

“…For example, the spin-driven Jahn-Teller effect in the Cr spinel compounds CdCr 2 O 4 and ZnCr 2 O 4 acts to lift the degenerate ground state arising from competing magnetic interactions via a coupling to the lattice degrees of freedom; the ensuing lattice distortion is unambiguously observed in the infrared as a splitting of infrared-active phonon modes. 6,7 Furthermore, the a.c. electric (magnetic) field of the infrared light can interact with ordered moments and excite an electromagnon (magnon) excitation, which in turn can provide information about the symmetry and nature of the magnetic order. 8,9 Here we present our infrared studies on single crystal Cu 3 Bi(SeO 3 ) 2 O 2 Cl.…”