Signatures of magnetostriction and spin-phonon coupling in magnetoelectric hexagonal15R−BaMnO3

Abstract

Spin-phonon coupling, the interaction of spins with surrounding lattice is a key parameter to understand the underlying physics of multiferroics and engineer their magnetization dynamics. Elementary excitations in multiferroic materials are strongly influenced by spin-phonon interaction, making Raman spectroscopy a unique tool to probe these coupling(s). Recently, it has been suggested that the dielectric and magnetic properties of 15R-type hexagonal BaMnO3 are correlated through the spin-lattice coupling. Here, we report the observation of an extensive renormalization of the Raman spectrum of 15R-BaMnO3 at 230 K, 280 K, and 330 K. Magnetic measurements reveal the presence of a long-range and a short-range magnetic ordering in 15R-BaMnO3 at 230 K and 330 K, respectively. The Raman spectrum shows the appearance of new Raman modes in the magnetically ordered phases. Furthermore, an additional Raman phonon appears below ~ 280 K, possibly arising from a local latticedistortion due to the displacement of Mn-ions, that exhibits anomalous shift with temperature. The origin of the observed renormalization and phonon anomalies in Raman spectra are discussed based on the evidences from temperature-and magnetic-field-dependent Raman spectra, temperature-dependent x-ray diffraction, magnetization, and specific heat measurements. Our results indicate the presence of magnetostriction and spin-phonon coupling in 15R-BaMnO3 thus suggesting that the optical phonons are strongly correlated to its magnetoelectric properties.

Spin-Phonon Coupling in Iron-Doped Ultrathin Bismuth Halide Perovskite Derivatives

“…Overall, the magnetic-field-induced frequency shifts are indications of the magnitude of spin-phonon coupling strengths of each mode. We postulate that when the applied field modifies the orientation and interaction of spins, the interatomic spring constants and the frequency of each mode changes accordingly, in a similar mechanism as the static magnetostriction effect. , Although nonmagnetic materials may also exhibit finite magnetostriction, , the observed large magnitude of phonon softening on the order of 0.1% above 4T is more consistent with the materials’ strong spin exchange interaction and magnetic order. , We have not observed any saturation or hysteresis in either the helicity or the intensity of the field-dependent Raman spectra, implying that the spin order, if any, is unlikely to be ferromagnetism. This agrees with the antiferromagnetic exchange between iron spins observed in pure Cs 3 Fe 2 Br 9 , but the onset of spin correlation occurs at a much higher temperature in doped ultrathin films than pure crystals .…”

“…We postulate that when the applied field modifies the orientation and interaction of spins, the interatomic spring constants and the frequency of each mode changes accordingly, in a similar mechanism as the static magnetostriction effect. 37,38 Although nonmagnetic materials may also exhibit finite magnetostriction, 39,40 the observed large magnitude of phonon softening on the order of 0.1% above 4T is more consistent with the materials' strong spin exchange interaction and magnetic order. 41,42 We have not observed any saturation or hysteresis in either the helicity or the intensity of the field-dependent Raman spectra, implying that the spin order, if any, is unlikely to be ferromagnetism.…”

Magnetostriction of α-RuCl3 flakes in the zigzag phase

“…A non-reciprocal magneto-phonon interaction was also reported for CrI 3 in the form of polarization rotation asymmetric with magnetic field 43 , but little to negligible shift of the vibrational Raman modes was described in that report. In addition to CrI 3 , Raman frequency shifts in response to magnetic field have been observed in 15R-BaMnO 3 44 . The hysteretic shifts in α-RuCl 3 Raman modes reported here are statistically significant, but highly variable.…”

Lattice dynamics of BaFe2Se3

“…Even-though BaFe 2 Se 3 is only superconducting under pressure and at low temperature, the possibility of a spin-lattice coupling stronger than first expected need to be investigated. Indeed, growing number of works have recently accessed the importance of spin-lattice coupling in strongly correlated systems [29][30][31].…”