Abstract-Ultralow temperature terahertz magnetic thermodynamics of perovskite-like SmFeO3 ceramic.

Xiaojian Fu, Xinxi Zeng, Dongyang Wang, Hao Chi Zhang, Jiaguang Han, Tie Jun Cui

http://www.pubfacts.com/detail/26424488/Ultralow-temperature-terahertz-magnetic-thermodynamics-of-perovskite-like-SmFeO3-ceramic

The terahertz magnetic properties of perovskite-like SmFeO3 ceramic are investigated over a broad temperature range, especially at ultralow temperatures, using terahertz time-domain spectroscopy. It is shown that both resonant frequencies of quasi-ferromagnetic and quasi-antiferromagnetic modes have blue shifts with the decreasing temperature due to the enhancement of effective magnetic field. The temperature-dependent magnetic anisotropy constants are further estimated using the resonant frequencies, under the approximation of omitting the contribution of Sm(3+) magnetic moments to the effective field. Specially, the effective anisotropy constants in the ca and cb planes at 3 K are 6.63 × 10(5) erg/g and 8.48 × 10(5) erg/g, respectively. This thoroughly reveals the terahertz magnetic thermodynamics of orthoferrites and will be beneficial to the application in terahertz magnetism.

Abstract-Anisotropic terahertz dielectric responses of sodium nitrate crystal

Xiaojian Fu,   Youting Song,   Chang Qing Sun and   Ji Zhou  

Phys. Chem. Chem. Phys., 2014, Accepted Manuscript

DOI: 10.1039/C3CP55484H
Received 28 Dec 2013, Accepted 18 Feb 2014
First published online 18 Feb 2014
http://pubs.rsc.org/en/content/articlelanding/2014/cp/c3cp55484h#!divAbstract

Terahertz (THz) spectroscopy has become an effective tool to characterize the low-frequency rotational and vibrational modes of molecules. In addition, novel THz dielectric responses and optical properties on the basis of molecular rotation and vibration have attracted lots of attention because of their potential application in THz devices. In this paper, the dielectric response of low-symmetric sodium nitrate crystal in the frequency range of 0.2-1.5 THz was experimentally demonstrated. Four absorption bands at 0.23, 0.47, 0.92, and 1.15 THz were observed in the dielectric spectra and were tentatively ascribed to the rotational motion of nitrate ions. Based on the molecular rotation mechanism, the dielectric anisotropy and dielectric resonance of the crystal were discussed in detail.

Abstract-Molecular Rotation-Vibration Dynamics of Low-Symmetric Hydrate Crystal in the Terahertz Region

Xiaojian Fu , Hongya Wu , Xiaoqing Xi , and Ji  Zhou

J. Phys. Chem. A, Just Accepted Manuscript

DOI: 10.1021/jp411609t

Publication Date (Web): December 22, 2013

Copyright © 2013 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/jp411609t?journalCode=jpcafh

The rotational and vibrational dynamics of molecules in copper sulfate pentahydrate crystal are investigated with terahertz dielectric spectra. It is shown that the relaxation-like dielectric dispersion in the low frequency region is related to the reorientation of water molecules under the driving of terahertz electric field, whereas the resonant dispersion can be ascribed to lattice vibration. It is also found that, due to the hydrogen-bond effect, the vibrational mode at about 1.83 THz along [-111] direction softens with decreasing temperature, that is, the crystal expands in this direction when cooled. On the contrary, the mode hardens in the direction perpendicular to [-111] during the cooling process. This contributes to the further understanding of the molecular structure and bonding features of hydrate crystals.