Abstract-Terahertz time-domain spectroscopy for magnonics and magnetotransport

Zuanming Jin, Xiumei Liu, Shunnong Zhang, Wanying Zhao, Xian Lin, Zongzhi Zhang, Chao Jin, Shixun Cao, Zhenxiang Cheng, Guohong Ma, Jianquan Yao,

https://www.osapublishing.org/abstract.cfm?uri=ISUPTW-2018-ThD2

Terahertz (THz) time-domain spectroscopy can be used to investigate the spintronic effects, such as low-energy magnons and magnetotransports, in the ultrafast operation regime, sub-picosecond time scale and/or terahertz frequency range.

© 2018 OSA

Abstract-Photoinduced terahertz radiation and negative conductivity dynamics in Heusler alloy Co2MnSn film

Shunnong Zhang, Zuanming Jin, Xiumei Liu, Wanying Zhao, Xian Lin, Chao Jing, and Guohong Ma

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-42-16-3080&origin=search

We report the broadband terahertz (THz) radiation in ferromagnetic half-metallic Heusler alloy Co2MnSn${\mathrm{Co}}_2\mathrm{MnSn}$ thin film upon the irradiation of a femtosecond laser pulse at room temperature. The magnetic-, sample symmetry-, and pump fluence-dependent THz emission reveals that the THz radiation is originated from the magnetic-dipole radiation, i.e., the light-induced subpicosecond demagnetization. In addition, by optical pump-THz probe spectroscopy, we found that the photoexcited increase of the scattering rate of hot carriers thereby leads to the photoinduced negative THz conductivity in Co2MnSn${\mathrm{Co}}_2\mathrm{MnSn}$ thin film.

© 2017 Optical Society of America

Abstract-Photo-Induced Terahertz Conductivity and Carrier Relaxation in Thermal-Reduced Multilayer Graphene Oxide Films

Xiao Xing, Litao Zhao, Zeyu Zhang, Liang Fang, Zhengfu Fan, Xiumei Liu, Xian Lin, Jianhua Xu, Jinquan Chen, Xinluo Zhao, Zuanming Jin, and Guo-Hong Ma

J. Phys. Chem. C, Just Accepted Manuscript

DOI: 10.1021/acs.jpcc.6b10580

Publication Date (Web): January 11, 2017

Copyright © 2017 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/acs.jpcc.6b10580?journalCode=jpccck

Graphene oxide (GO) is an attractive option for large scale production of graphene. On the other hand, the graphene obtained by the reduction of GO has inevitable structural defects, and the vacant lattice sites will significantly restrict its conductivity. It has been demonstrated that thermal annealing in hydrogen is an efficient method to reduce defects and heal the lattice in GO samples. However, it is still not clear that how the defects and/or disordering influence on the photoelectric conversion efficiency and the carrier relaxation pathway in GO. Herein, the time-domain terahertz (THz) spectroscopy is employed to characterize the properties of the multilayer GO films which were annealed in hydrogen at various temperatures. Upon photo excitation, a transient increase of the conductivity was observed for the reduced graphene oxide (RGO) samples. The ultrafast carrier relaxation process can be well assigned to the carrier-carrier scattering and carrier-phonon coupling. Our results demonstrated that the RGO films with fewer defects and better lattice structure is successfully manufactured. In addition, by fitting to the Drude model, several electron transport parameters, such as the carrier scattering time, carrier plasma frequency and photoinduced conductivity, are obtained in our multilayer RGO films.

Abstract-Resolving the spin reorientation and crystal-field transitions in TmFeO3 with terahertz transient

• Kailin Zhang
• , Kai Xu
• , Xiumei Liu
• , Zeyu Zhang
• , Zuanming Jin
• , Xian Lin
• , Bo Li
• , Shixun Cao
•  &Guohong Ma

http://www.nature.com/articles/srep23648
Rare earth orthoferrites (RFeO3) exhibit abundant physical properties such as, weak macroscopic magnetization, spin reorientation transition, and magneto-optical effect, especially the terahertz magnetic response, have received lots of attention in recent years. In this work, quasi-ferromagnetic (FM) and quasi-antiferromagnetic (AFM) modes arising from Fe sublattice of TmFeO3 single crystal are characterized in a temperature range from 40 to 300 K, by using terahertz time-domain spectroscopy (THz-TDS). The magnetic anisotropy constants in ac-plane are estimated according to the temperature-dependent resonant frequencies of both FM and AFM modes. Here, we further observe the broad-band absorptions centered ~0.52, ~0.61, and ~1.15 THz below 110 K, which are reasonably assigned to a series of crystal-field transitions (R modes) of ground multiplets (6H3) of Tm3+ ions. Specially, our finding reveals that the spin reorientation transition at a temperature interval from 93 to 85 K is driven by magnetic anisotropy, however, which plays negligible role on the electronic transitions of Tm ions in the absence of applied magnetic fields.