arXiv subjects

S. A. Klimin

Publications and source records attributed to S. A. Klimin.

4 recordsLinked to original sources

arXiv2026

The ground ytterbium doublet in h-YbMnO3 and the related low-temperature peculiarities of the compound

We have performed detailed temperature-dependent study of optical f-f transitions of the Yb3+ ions in h-YbMnO3 by means of Fourier-transform spectroscopy. The splitting of the ground Kramers doublet as a function of temperature, D0(T), for the Yb3+ ion at 4b site was determined. The D0(T) function follows the dynamics of the manganese magnetic moment below TN = 87 K, indicating, that the ytterbium subsystem is magnetized by the magnetic field generated by an ordered manganese subsystem, which is consistent with the results of previous studies. Excitation of the upper component of the split ground doublet plays a significant role in low-temperature dynamics of the h-YbMnO3 crystal. Using the D0(T) function we calculated the temperature behavior of the of the Yb(4b) magnetic moment: it is in clear agreement with the neutron data [Phys. Rev. B 98, 134413, 2018]. The calculated contribution of Yb(4b) to heat capacity definitely explains the origin of the Schottky anomaly in the CP(T) dependence. A scenario for phase transitions in h-YbMnO3 is proposed in which the energy gain in the ytterbium system plays a key role.

cond-mat.str-el↗

arXiv2016

Probing Dy3+ magnetic moments in multiferroic perovskite DyMnO3 by optical spectroscopy

We present a detailed temperature-dependent spectroscopic study of DyMnO3 single crystals with distorted perovskite structure. Energies of 36 crystal-field levels of Dy3+ in paramagnetic DyMnO3 were determined. The Dy3+ ground Kramers doublet does not split at T_N^Mn = 39 K and splits below Tlock = 18 K. The splitting grows fast at temperatures near T_N^Dy = 6.5 K and reaches Δ0 = 11 cm-1 at 4 K. Using the experimental temperature dependence Δ0(T), we calculate the dysprosium magnetic moment mDy(T) and the dysprosium contribution into specific heat and magnetic susceptibility. Analysing all the experimental data, we conclude that the Dy-Mn interaction is of the Dzyaloshinskii-Moriya type.

cond-mat.str-el↗

arXiv2015

Infrared study of lattice dynamics and spin-phonon and electron-phonon interactions in multiferroic TbFe3(BO3)4 and GdFe3(BO3)4

We present a comparative far-infrared reflection spectroscopy study of phonons, phase transitions, spin-phonon and electron-phonon interactions in isostructural multiferroic iron borates of gadolinium and terbium. The behavior of phonon modes registered in a wide temperature range is consistent with a weak first-order structural phase transition (Ts = 143 for GdFe3(BO3)4 and 200 K for TbFe3(BO3)4) from high-symmetry high-temperature R32 structure into low-symmetry low-temperature P3121 one. The temperature dependences of frequencies, oscillator strengths, and damping constants of some low-frequency modes reveal an appreciable lattice anharmonicity. Peculiarities in the phonon mode behavior in both compounds at the temperature of an antiferromagnetic ordering (TN = 32 K for GdFe3(BO3)4 and 40 K for TbFe3(BO3)4) evidence the spin-phonon interaction. In the energy range of phonons, GdFe3(BO3)4 has no electronic levels but TbFe3(BO3)4 possesses several ones. We observe an onset of new bands in the excitation spectrum of TbFe3(BO3)4, due to a resonance interaction between a lattice phonon and 4f electronic crystal-field excitations of Tb3+. This interaction causes delocalization of the CF excitations, their Davydov splitting, and formation of coupled electron-phonon modes.

cond-mat.str-el↗

arXiv2001

Lattice vibrations of alpha'-NaV_2O_5 in the low-temperature phase. Magnetic bound states?

We report high resolution polarized infrared studies of the quarter-filled spin ladder compound alpha'-NaV_2O_5 as a function of temperature (5K <= T <= 300K). Numerous new modes were detected below the temperature T_c=34K of the phase transition into a charge ordered nonmagnetic state accompanied by a lattice dimerization. We analyse the Brillouin zone (BZ) folding due to lattice dimerization at T_c and show that some peculiarities of the low-temperature vibrational spectrum come from quadruplets folded from the BZ point (1/2, 1/2, 1/4). We discuss an earlier interpretation of the 70, 107, and 133cm-1 modes as magnetic bound states and propose the alternative interpretation as folded phonon modes strongly interacting with charge and spin excitations.

cond-mat.str-el↗