V. D. Travkin

Evidence for Electroactive Excitation of the Spin Cycloid in TbMnO3

Terahertz electromagnetic excitations in the multiferroic TbMnO3 single crystals are investigated across the magnetic field induced rotation of the magnetic spin cycloid. In addition to the electromagnon along the a axis, the detailed polarization analysis of the experimental spectra suggests the existence of an electroactive excitation for ac electric fields of the electromagnetic wave along the crystallographic c axis. This excitation is possibly the electroactive eigenmode of the spin-cycloid in TbMnO3, which has been predicted within the inverse Dzyaloshinskii-Moriya mechanism of magnetoelectric coupling.

Magnetic, dielectric, and transport properties of La1−xSrxMnO3 at submillimeter wavelengths

Antiferromagnetic resonance (AFMR), dynamic conductivity, and dielectric permittivity have been studied in the La1−xSrxMnO3 perovskites at a frequency range of ν=3–33 cm−1 by the use of a quasi-optical backward-wave-oscillator technique. Two AFMR modes have been observed in LaMnO3 and La0.95Sr0.05MnO3. Temperature dependencies of their resonance frequencies, linewidths, and mode contributions to a static magnetic permeability have been obtained and corresponding parameters of magnetic interactions have been extracted. A jump in the dielectric permittivity e′(T) was found at T=100–120 K in La0.9Sr0.1MnO3, which indicates the existence of an additional phase transition (probably, a polaron ordering) besides the ferromagnetic transition at 170 K. A sharp increase of the dynamic conductivity σ′(ν,T) was observed near Curie temperature (285 K) at a metal–semiconductor transition in La0.825Sr0.175MnO3, which was slightly smaller than its static value.

Magnetic and structural transitions in La1−x Sr x MnO3: T-x phase diagram

The electrical conductivity, magnetic susceptibility, magnetization, and submillimeter (v=5∓20 cm−1) permittivity and dynamic conductivity of La1−xSrxMnO3 (0≤x≤ 0.45) single crystals are investigated. The anomalies in the temperature dependences of these quantities are identified with diverse magnetic and structural phase transformations, including antiferromagnetic and ferromagnetic ordering, structural transitions between strongly distorted (Jahn-Teller) and weakly distorted (pseudocubic) orthorhombic phases, structural transitions to a rhombohedral phase and unusual transitions to a polaron-ordering state. As a result, the complete T-x phase diagram of the system La1−2xSrxMnO3 is constructed in a wide interval of temperatures T=4.2∓1050 K and concentrations x=0−0.45.

Magnetic and Magnetoelectric Excitations in TbMnO3

Magnetic and magnetoelectric excitations in the multiferroic TbMnO3 have been investigated at terahertz frequencies. Using different experimental geometries we can clearly separate the electroactive excitations (electromagnons) from the magnetoactive modes, i.e., antiferromagnetic resonances. Two antiferromagnetic resonances were found to coincide with electromagnons. This indicates that both excitations belong to the same mode and the electromagnons can be excited by a magnetic ac field as well. In spite of the 90 degrees rotation of the magnetic cycloid in external magnetic fields, the electromagnons are observable for electric ac fields parallel to the a axis only.

Terahertz spectroscopy of electromagnons in Eu1 xYxMnO3

Dielectric permittivity spectra of yttrium-doped

Phase T–x diagram of Sm1−xSrxMnO3 single crystals (0⩽x⩽0.8)

\mathrm{Eu}\mathrm{Mn}{\mathrm{O}}_{3}

Soft-mode behavior of electromagnons in multiferroic manganite

in the composition range

Magnetic and submillimeter spectroscopy study of phase transitions in La1-xSrxMnO3 perovskites : T-x phase diagram

0\ensuremath{\leqslant}x\ensuremath{\leqslant}0.5

Phase transitions and spin excitations in new multiferroics with modulated magnetic structure

have been investigated in the terahertz frequency range. Magnetoelectric contributions to the permittivity were observed in all compositions for ac electric fields parallel to the crystallographic

AFMR and magnetic anisotropy in Y1-xLuxFeO3 orthoferrites

a