Negative refractions of acoustic waves in a two-dimensional (2D) sonic crystal were studied both experimentally and theoretically. By calculating the acoustic band structure and equifrequency surfaces, we theoretically analyzed the acoustic single-beam negative refraction in the first band operating in the ultrasonic regime. A 2D square sonic crystal was constructed with 2.0-mm-diam steel cylinders arranged as square arrays of 2.5mm lattice constant. A scanning transmission measurement of spatial distribution was carried out to establish the acoustic refraction of a single Gaussian beam. It was demonstrated that the negative refraction is strongly dependent on both frequencies and incident angles, which shows great potential in acoustic devices.

Phonon-polaritons are studied both theoretically and experimentally in a one-dimensional two-component generalized quasiperiodic piezoelectric superlattice. The experimental observation of phonon-polaritons through dielectric abnormality is carried out at the microwave region. Some potential applications are discussed.

To realize the hole-mediated ferromagnetism, manganese and nitrogen-codoped ZnO(Zn1-xMnxO:N) films were prepared on sapphire (0001) by reactive radio-frequency (rf) magnetron sputtering from Zn0.97Mn0.03O ceramic targets using N2 gas. X-ray photon spectra reveal that the doped Mn ions are mainly in divalent states and the coexistence of O-Zn and N-Zn bonds in the films. According to the absorption spectra, the band gap of Zn0.97Mn0.03O: N films is about 3.15eV, which is slightly lower than that of ZnO films (3.20eV). Compared with Zn0.97Mn0.03O films, ferromagnetic behavior of Zn0.97Mn0.03O: N films were significantly changed with a coercivity of about 70 Oe, a saturation magnetization of 0.92μB/Mn2) and a remanance over 0.15μB/Mn2) at 300K, while at 10K, they increased to be about 110 Oe, 1.05μB/Mn2) and 0.23μB/Mn2), respectively. However, rapid thermal annealing treatment in pure oxygen results in a significant decrease on the magnetic properties of the films.