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RFeO3 is an ideal candidate for the fabrication of spintronic devices, and its rare earth site doping is an important means to regulate and produce many unique spin behaviors. In this work, we report a high-quality Dy0.5Tb0.5FeO3 single crystal grown by optical floating zone method and its magnetic properties are studied explicitly. A type Ⅱ spin switching effect and suppressed spin reorientation transition are found in the Magnetization vs Temperature curves in Dy0.5Tb0.5FeO3. In the temperature region of spin reorientation transition, the transition of Fe3+ magnetic sublattice configuration becomes very complicated by the influence of competitive interaction with magnetic Dy3+/Tb3+ ions. Interestingly, a field tunable double-hysteresis loop is observed near the antiferromagnetic transition temperature of rare earth ions sublattice, which has never been reported in RFeO3 family compounds. By studying the dependence of double-hysteresis loop at different temperatures, the magnetic phase transition and spin reorientation transition induced by the applied magnetic field is inferred. This novel physical phenomenon helps us understand the mechanism of spin configuration transition better at low temperatures.

PrF3 crystals are excellent paramagnetic magneto-optical materials. In this paper we report on the PrF3 complex refractive index and the complex permittivity in terahertz (THz) frequency range. Measurements have been performed using transmission time domain terahertz spectroscopy (THz-TDS). The influence of temperature on the complex refractive index and the complex permittivity was also investigated. To the best of authors knowledge this dependency have not been reported thus far. We show that complex refractive index increases with temperature (50 K–170 K), so do the values of complex permittivity and loss tangent. A relatively small (~0.02) increase of loss tangent value is obtained for all frequencies (0.4THz-1.4 THz) at 170 K contrary to 50 K. It's worth mentioning the permittivity of PrF3 exhibits better thermal stability than CeF3 between 0.75 THz and 0.9 THz. Our research shows PrF3 is an excellent candidate for optoelectronic tunable application in THz frequency, especially between 0.75 THz and 0.9 THz when the temperature varies dramatically.

We present experimental observations of the high-performance magneto-optic (MO) CeF3 crystal using terahertz time-domain spectroscopy (THz-TDS) in the temperature range 40–300 K for the first time. The complex refractive index strongly depends on temperature, which increases with increasing temperature. Intriguingly, the changes of complex refractive index values reach more than 0.1 between 40 K and 300 K, which is larger than terbium scandium aluminum garnet (TSAG) crystal. The weak loss tangent indicates that the crystal has a high potential as a high-dielectric-constant photovoltaic device in the terahertz domain.

The electron spin coherences in colloidal CdSe quantum dots with zinc blende structure are investigated by using ultrafast time-resolved Faraday ellipticity at room temperature. Particle size and magnetic field dependences of spin coherence indicate that the spin coherence is originated from the residual spin polarized electrons due to the exchange flip–flop scattering. The external magnetic field dependence of electron spin dephasing time suggests that the main limiting factor for the dephasing is the spread of electron spin Larmor precession frequency. In addition, the size dependence of electron g -factor in zinc blende CdSe quantum dots is determined to increase from 1.64 to 1.71 with decreasing diameters of quantum dots from 5.8 to 4.0 nm.

The ultrafast third-order nonlinear optical properties of an azobenzene-containing ionic liquid crystalline polymer were investigated by optical Kerr effect (OKE) and pump–probe techniques with femtosecond pulses. The third-order nonlinear optical susceptibility of the sample solution was obtained to be 2.1 × 10−14 esu at a concentration of 2 × 10−3 M. The temporal response of the sample solution was decomposed into two components, which could be explained by the relaxation of different singlet excited states. The polymer thin film exhibited strong ultrafast nonlinear optical response of 8.26 × 10−10 esu and show its potential applications for further nonlinear optical devices.

Optical pump-terahertz probe spectroscopy is employed to investigate the optical characteristics of silicon wafer. The wafer surface undergoes a phase transition from insulator to metal for terahertz wave with increasing pump fluence. The real part of the pump-induced conductivity shows strong frequency dependence, which can be well described with Drude–Smith model. Our results also demonstrate that the photoexcited Si layer acts as a broadband terahertz pulse antireflection coating with proper pump fluence. In addition, it is observed that the terahertz pulse apparently arrives at the detector earlier when silicon is optically excited.