Lower Resonant Mode Research Articles

Ammonium resonance modes and orientational glass state in the K1-X(NH4)XI mixed crystals

The behaviour of ammonium ions in the mixed crystals of alkaline metal-ammonium halides until present time are not fully understood. There are the observations at low temperature of the low energy resonance modes in the disordered α-phase of the K1-x(NH4I mixed crystals which are observed also in orientational glass state of this phase. However, low energy resonance modes are not observed in the low temperature ordered phases of these mixed crystals. The identification of the origin of the resonance modes in the K0.55(NH4)0.45I mixed crystal was carried out with the help of the inelastic incoherent neutron scattering from protonated and deuterated samples. It was shown that these modes can be treated as translational. The study also was carried out of the influence of the transfer from the static orientationally disordered glass state into die dynamic orientationally disordered state in the α-phase of protonated K0.55(NH4)0.45I mixed crystal with the temperature increase on the evolution of the inelastic incoherent neutron scattering intensity.

Lower hybrid resonant layer excitation and mode conversion in the linear LISA machine

The radio frequency absorption near the lower hybrid resonance of an inhomogeneous plasma has been studied using Langmuir and magnetic probes and also a Faraday cup. The plasma was confined in the mirror linear device LISA, excited by a 28 MHz RF source. It has been shown that the absorption rate and the resonance region in space depends on the resonant volume created by the external magnetic field. Due to the collisional damping, the quality factor of the machine is comparable to a low-Q cavity resonator.

Interlayer exchange coupling study of Ni 80Fe 20/Cr multilayered structures

The evidences of antiferromagnetic interlayer exchange coupling in Ni 80Fe 20/Cr multilayered structures were reported. In Ni 80Fe 20/Cr multilayered structures, both the magnitude of the interlayer magnetic exchange coupling and the saturation magnetoresistance have been found to oscillate with the Cr spacer layer thickness with a period of about 13 Å. Ferromagnetic resonance (FMR) spectra have revealed that for antiferromagnetically (AF) coupled films ( t Cr = 12, 25 A ̊ ) there is a weak absorption mode of higher field than that of the regular in-phase mode, and that there are only some lower field resonance modes for ferromagnetically coupled films. Moreover, the magnetization vs temperature curves for the AF films have been found to have sizable thermal magnetic hysteresis. From the FMR spectrum for t Cr = 12 A ̊ and the temperature dependence of the magnetization in different magnetic fields for t Cr = 12, 25 A ̊ , the maximum strength of the AF coupling has been estimated to be about 0.017 erg cm -2.

VIBRATION PROPERTIES OF IMPURITIES IN ZINCBLENDE STRUCTURE

The phonon spectra of substitutional impurities in zincblende structure are calculated. The form law and characteristics for imparity induced local modes, gap modes and resonant modes are analyzed systematically. Besides the quasi-local mode above TA acoustic band, we also find a new low frequncy resonant mode just below TA acoustic band.

Extensional Effects in Constrained Viscoelastic Layer Damping

SummaryThe vibration damping in unsymmetrical, multi-layer beams is obtained by the combined effects of extensional and shear stresses in the viscoelastic layer. The shear stress distribution is not constant across such a layer, although previous work has ignored this. The error in an estimate based on the previous work of the overall loss factor can be large, in particular for the lower resonant modes of long beams with a stiff damping layer.