Phonons and Magnetic Excitations in Mott-Insulator LaTiO$_3$

We report a neutron and Raman scattering study of a single-crystal of La(2)CuO(4.05) prepared by high temperature electrochemical oxidation. Elastic neutron scattering measurements show the presence of two phases, corresponding to the two edges of the first miscibility gap, all the way up to 300 K. An additional oxygen redistribution, driven by electronic energies, is identified at 250 K in Raman scattering (RS) experiments by the simultaneous onset of two-phonon and two-magn...

We report the evolution of the Raman active A_g phonon modes in the charge-ordered manganite Pr_{0.63}Ca_{0.37}MnO_{3} as a function of temperature from 300K to 25K. Our studies reveal that the linewidths of A_g(2) and A_g(4) phonons increase as temperature decreases. This anomalous temperature dependence of phonon lineshapes, seen for the first time in charge ordered manganites, can be quantitatively understood in terms of strong spin-phonon coupling involving t_{2g} spins a...

For CaCu$_{3}$Ti$_{4}$O$_{12}$ -- an insulator that exhibits a giant dielectric response above 100 K -- Cu$^{2+}$ antiferromagnetic spin ordering has been investigated by magnetic Raman scattering and magnetization measurements. Below the N\'eel temperature, T$_{N} = 25$ K, magnetic excitations have been identified. Above T$_{N}$ Raman spectra reveal short-range antiferromagnetic fluctuations that increase with cooling like T$^{-1}$. No deviations from Curie-Weiss law have be...

Achieving parametric excitation in an oscillating physical system involves periodically adjusting one of its parameters to modulate the oscillator's natural frequency. This phenomenon has been observed in numerous systems within physics and engineering, profoundly transforming modern science and technology. Despite rapid progress, the parametric control of collective excitations, such as phonons, remains a challenge while promising to generate novel and intriguing effects in ...

A theory of the anisotropic superexchange and low energy spin excitations in a Mott insulator with t_{2g} orbital degeneracy is presented. We observe that the spin-orbit coupling induces frustrating Ising-like anisotropy terms in the spin Hamiltonian, which invalidate noninteracting spin wave theory. The frustration of classical states is resolved by an order from disorder mechanism, which selects a particular direction of the staggered moment and generates a quantum spin gap...

We investigate the electronic and magnetic properties as well as lattice dynamics and spin-phonon coupling of $\beta$-Na$_{0.33}$V$_2$O$_5$ using temperature-dependent Raman scattering, dc-magnetization and dc-resistivity, x-ray photoemission, and absorption spectroscopy. The Rietveld refinement of XRD pattern with space group C2/m confirms the monoclinic structure. The analysis of temperature-dependent Raman spectra in a temperature range of 13--673~K reveals an anharmonic d...

Rare-earth orthoferrites are a promising platform for antiferromagnetic spintronics with a rich variety of terahertz spin and lattice dynamics phenomena. For instance, it has been experimentally demonstrated that the light-driven optical phonons can coherently manipulate macroscopic magnetic states via nonlinear magnetophononic effects. Here using TbFeO$_{3}$ as an example, we reveal the origin of the mode mixing between the LO and TO phonons, which is important for understan...

Antiferromagnetic materials with strong spin-phonon coupling have the potential for spintronic applications. Here, we report the structural, magnetic, and vibrational properties of 12R-BaTi0.4Mn0.6O3. Temperature-dependent magnetization data show the presence of weak antiferromagnetic interactions. Correlation between magnetic and vibrational properties are probed by using temperature-dependent Raman spectroscopic measurements. Two of the Raman active phonons show deviation f...

Raman scattering is an excellent method for simultaneously determining the dynamics of lattice, spin, and charge degrees of freedom. Furthermore, polarization selection rules in Raman scattering enable momentum-resolved quasiparticle dynamics. In this review, we highlight the potential of Raman scattering in probing magnetic quasiparticles or excitations in various magnetic materials. We demonstrate how temperature-dependent Raman scattering data can confirm the existence of ...

We have performed Raman scattering investigations on the high energy magnetic excitations in a BiFeO$_3$ single crystal as a function of both temperature and laser excitation energy. A strong feature observed at 1250 cm$^{-1}$ in the Raman spectra has been previously assigned to two phonon overtone. We show here that its unusual frequency shift with the excitation energy and its asymmetric temperature dependent Fano lineshape reveal a strong coupling to magnetic excitations. ...