Spin reorientation transition and coupled spin-lattice dynamics of Sm0.6Dy0.4FeO3.

In this work, we have presented a solid-solution of Sm0.6Dy0.4FeO3 in the form of nano-particles having spin reorientation transition (SRT) at a temperature interval of 220-260 K. The lattice dynamics of Sm0.6Dy0.4FeO3 have investigated by temperature-dependent x-ray diffraction and Raman spectroscopy. A negative thermal expansion at low temperatures has observed, which might be due to the interaction between Sm3+ and Fe3+ sublattice. Anomalous behavior in lattice parameters, octahedral tilt angle, and bond lengths have observed in the vicinity of SRT, which confirms the existence of magneto-elastic coupling in the system. The strong anomaly has observed in linewidth and phonon frequencies of Raman modes around SRT, which may be related to the spin-phonon coupling in Sm0.6Dy0.4FeO3. The contribution of SRT in lattice change and the presence of spin-phonon coupling can help to understand the correlation between the magnetic and structural properties of orthoferrite.

Effect of Yb doping on the refractive index and thermo-optic coefficient of YVO4 single crystals.

Single crystals of YVO4 with different doping concentrations of Yb (1.5, 3.0, 8.0, and 15.0 at. %) and with good crystalline quality (FWHM ∼43-55 arc sec of rocking curve) were grown by the optical floating zone technique. Refractive index measurements were carried out at four wavelengths as a function of temperature. The measurements show that as the doping concentration of Yb is increased, the refractive index varies marginally for ne whereas there is a significant change in the value of no. The thermo-optic coefficient (dn/dT) was found to be positive with a value ∼10-5/°C, which is 1 order higher than that for the undoped YVO4 crystal. The thermo-optic coefficient is higher for ne compared to that of no. Also, a set of relations describing the wavelength dependence of the thermo-optic coefficient were established that are useful for calculating the thermo-optic coefficient at any temperature in the range 30°C-150°C and at any wavelength in the range 532-1551 nm.

Temperature-dependent index of refraction of monoclinic Ga2O3 single crystal.

We present temperature-dependent refractive index along crystallographic b[010] and a direction perpendicular to (100)-plane for monoclinic phase (ß) Ga(2)O(3) single crystal grown by the optical floating zone technique. The experimental results are consistent with the theoretical result of Litimein et al.1. Also, the Sellmeier equation for wavelengths in the range of 0.4-1.55 µm is formulated at different temperatures in the range of 30-175 °C. The thermal coefficient of refractive index in the above specified range is ~10(-5)/°C.

Development of a versatile high temperature top seeded solution growth unit for growing cesium lithium borate crystals.

The design and fabrication of a state of the art high temperature top seeded solution growth (HTTSSG) unit with seed and crucible rotation options is discussed. Crystals from solid solutions of high viscosity could be grown using the setup. The fabricated setup is used to grow high optical quality single crystals of cesium lithium borate with dimensions 50x40x40 mm(3) for frequency conversion of ir to UV laser through harmonic generation.