Far-infrared spectra of the magnetic exchange resonances and optical phonons and their connection to magnetic and dielectric properties of Dy3Fe5O

Abstract

Far-infrared spectra of ferrimagnetic Dy 3 Fe 5 O 12 single crystals have been studied in the spectral range between 12 and 700 cm -1 and in a wide temperature range between 5 K and 300 K using transmission spectroscopy and rotating analyzer ellipsometry. In the temperature range below T C =16 K for the magnetic ordering of Dy 3+ spins, a number of ligand field (LF) and Kaplan-Kittel (KK) exchange resonance modes have been found. Temperature dependences of their frequencies allowed us to estimate the ratio between the Fe−Dy and Dy−Dy exchange constants.We found that variation of the oscillator strength of the KK modes correlates with the magnetic field induced changes of magnetic permeability. The low temperature peak in the static value of the dielectric function at T C =16 K may be related to the observed temperature-induced variation of the oscillator strength of the optical phonons.

Terahertz Vortex Beam as a Spectroscopic Probe of Magnetic Excitations

“…The experimental temperature dependencies of the LF and KK excitations in Dy-IG ( Fig. 3) are similar to that for antiferromagnetic resonances, or magnons at ⃗ k ¼ 0, in the magnetically ordered system with several interacting spins [39][40][41]. Interaction of the LF and KK modes in Dy-IG with vortex optical beams is the main focus of our experiments.…”

“…Experimental data for energies of the LF, KK, and CF modes are shown with solid symbols. Data from Ref [39]. obtained with conventional linearly polarized light are shown with dashed curves for comparison.…”

Synchrotron radiation-based far-infrared spectroscopic ellipsometer with full Mueller-matrix capability

“…The far-IR properties of Dy-IG, such as the frequencies of the optical phonons and magnons, are well- known from the previous optical transmission and reflection experiments. 4,[68][69][70][71] Figure 7 shows broad range RAE spectra of Dy-IG measured between 30 and 4000 cm −1 at AOI = 75 • and T = 7 K. These spectra have been obtained using three sets of linear polarizers and three types of detectors: LHe-pumped (1.6 K) bolometer, LHe (4.2 K) bolometer, and CuGe detector. The low-frequency cutoff is determined by the diffraction limit due to the size of the available crystal of about 5 × 5 mm 2 .…”

“…The pure magnetic dipole excitation (magnon) appears at 59.5 cm −1 , which is exactly the same frequency as previously determined. 4,71 Pure electric dipole excitation at 81 cm −1 corresponds to the optical phonon. Our measurements demonstrate [see Fig.…”

Spin-phonon interactions of multiferroic Bi4Ti3O12-BiFeO3 ceramics: Low-temperature Raman scattering and infrared reflectance spectra investigations

“…Microscopic nature of the phase transition is required for the optimization of multiferroic properties, which can be better understood through the studies of optical excitations such as temperature dependent infrared active modes due to spin-lattice interaction. 9 However, few reports about thermal-optical responses and lattice vibrations of BTF ceramic during AFM to PM magnetic phase transition have been presented to date. As we know, both of Raman scattering and infrared reflectance spectra are nondestructive and attractive probe techniques, which are complementary and can provide some invaluable information on lattice vibrations and structural variations.…”