Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSmall influence of magnetic ordering on lattice dynamics in TaFe$_{1.25}$Te$_3$
175
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Raman scattering spectra of zigzag spin chain TaFe$_{1.25}$Te$_3$ single crystal are presented in a temperature range from 80 to 300 K. Nine Raman active modes of $A_g$ and $B_g$ symmetry are clearly observed and assigned by probing different scattering channels, which is confirmed by lattice dynamics calculations. Temperature dependence of the Raman modes linewidth is mainly governed by the lattice anharmonicity. The only deviation from the conventional behavior is observed for $A_g$ symmetry modes in a vicinity of the magnetic phase transition at $T_N approx 200$ K. This implies that the electron-phonon interaction weakly changes with temperature and magnetic ordering, whereas small changes in the spectra near the critical temperature can be ascribed to spin fluctuations.
rate research
Read More
The layered topological insulator MnBi$_2$Te$_4$ has attracted great interest recently due to its intrinsic antiferromagnetic order, potentially hosting various topological phases. By temperature-dependent infrared spectroscopy over a broad frequency range, we studied the changes in the optical conductivity of MnBi$_2$Te$_4$ at the magnetic ordering temperature. The temperature dependence of several optical parameters reveals an anomaly at the magnetic phase transition, which suggests the correlation between the bulk electronic band structure and the magnetism. We relate our findings to recent reports on the temperature dependence of the electronic band structure of MnBi$_2$Te$_4$.
The Born effective charges of component atoms and phonon spectra of a tetrahedrally coordinated crystalline ice are calculated from the first principles method based on density functional theory within the generalized gradient approximation with the projected augmented wave method. Phonon dispersion relations in a 3x1x1 supercell were evaluated from Hellmann-Feynman forces with the direct method. This calculation is an additional work to the direct method in calculating the phonon spectra which does not take into account the polarization charges arising from dipole interaction of molecules of water in ice. The calculated Born effective polarization charges from linear response theory are supplied as the correction terms to the dynamical matrix in order to further investigate the LO-TO splitting of the polar modes of ice crystal at k=0 which has long been speculated for this system especially in the region between 28 and 37 meV both in the theoretical and experimental studies. Our results clearly show the evidence of splitting of longitudinal and transverse optic modes at the k=0-point in agreement with some experimental findings.
We report on the influence of the improved L21 ordering degree on the magnetic properties of Co2MnSi Heusler films. Different fractions of the L21 phase are obtained by different post-growth annealing temperatures ranging from 350 degC to 500 degC. Room temperature magneto-optical Kerr effect measurements reveal an increase of the coercivity at an intermediate annealing temperature of 425 degC, which is a fingerprint of an increased number of pinning centers at this temperature. Furthermore, Brillouin light scattering studies show that the improvement of the L21 order in the Co2MnSi films is correlated with a decrease of the saturation magnetization by about 9%. The exchange stiffness constant of Co2MnSi, however, increases by about 8% when the L21 order is improved. Moreover, we observe a drop of the cubic anisotropy constant K1 by a factor of 10 for an increasing amount of the L21 phase.
We report a combined experimental and theoretical investigation of the magnetic structure of the honeycomb lattice magnet Na$_2$IrO$_3$, a strong candidate for a realization of a gapless spin-liquid. Using resonant x-ray magnetic scattering at the Ir L$_3$-edge, we find 3D long range antiferromagnetic order below T$_N$=13.3 K. From the azimuthal dependence of the magnetic Bragg peak, the ordered moment is determined to be predominantly along the {it a}-axis. Combining the experimental data with first principles calculations, we propose that the most likely spin structure is a novel zig-zag structure.
The different magnetic behaviors of LaCoO$_3$ films grown on LaAlO$_3$ and SrTiO$_3$ are related to the Co-O-Co bond angles and the constraints imposed on the Co-O bond lengths by the substrate geometries. Long-range magnetic order occurs below T ~ 90 K when the Co-O-Co bond angle is greater than 163 degrees, consistent with the behavior of bulk and nanoparticles forms of LaCoO$_3$. A LaAlO$_3$ substrate prevents magnetic long-range order at low temperatures near the film-substrate interface and collinear antiferromagnetic sublattices away from the interface. At low temperatures, the antiferromagnetically ordered sublattices are non-collinear in films grown on SrTiO$_3$ substrates, leading to a significant net moment.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
