Journal of the Korean Physical Society, Vol. 55, No. 1, July 2009, pp. 173∼176 Enhanced Phase Relaxation in a Hybrid Ferromagnet/Semiconductor System Kuang Yao Chen, Chun-Kai Yang and C.-T. Liang * Department of Physics, National Taiwan University, Taipei 106, Taiwan N. Aoki, Y. Ochiai † and Y. Ujiie Department of Electronics and Mechanical Engineering, Chiba University, Chiba 263, Japan K. A. Cheng Department of Electronic Engineering, Lung-Hwa University of Science and Technology, Taoyuan 333, Taiwan Li-Hung Lin Graduate Institute of Optoelectronics and Solid State Electronics, National Chiayi University, Chiayi 600, Taiwan C. F. Huang National Measurement Laboratory, Center for Measurement Standards, Industrial Technology Research Institute, Taiwan Yu-Ru Li and Yen Shung Tseng Department of Physics, National Taiwan University, Taipei 106, Taiwan Po-Tsun Lin Graduate Institute of Optoelectronics and Solid State Electronics, National Chiayi University, Chiayi 600, Taiwan Jau-Yang Wu and Sheng-Di Lin Department of Electronics Engineering, National Chiao Tung University, Hsinchu 300, Taiwan (Received 26 August 2008) Hybrid ferromagnet/semiconductor systems have been the focus of considerable attention because of the transport properties of two-dimensional electron systems and their potential applications to magnetic storage and sensing devices. We use the weak localization effect to probe the dephasing mechanism at low temperatures. In our study, the zero-temperature phase-relaxation rate can be enhanced in a hybrid ferromagnet/semiconductor system, which may be due to the inhomogeneous magnetic field emanating from the Ni film. The result may improve understanding of the issue of zero-temperature dephasing in disordered systems. PACS numbers: 73.43.Qt Keywords: Two-dimensional electron system, Hybrid ferromagnet/semiconductor system, Phase-relaxation rate I. INTRODUCTION Hybrid semiconductor/superconductor or semiconduc- tor/ferromagnetic systems have great potential applica- tions as magnetic storage and sensing devices [1,2] and have been attracting a great deal of interest [3,4]. Such a system is created by coating a superconducting or ferro- magnetic layer on top of a semiconductor structure. The * E-mail: ctliang@phys.ntu.edu.tw; † E-mail: ochiai@faculty.chiba-u.jp stray field from the top magnetic layer can greatly mod- ify the transport properties of the semiconductor system. One important transport parameter of a hybrid sys- tem is the phase-coherence time, τ φ , which describes how long a transport carrier can keep its phase “memory.” Conventionally, as the temperature approaches zero, the phase-coherence time is expected to become infinite, with only electron-electron and electron-phonon scattering. However, a finite saturated phase-coherence time at low temperatures was reported experimentally [5, 6]. The “zero temperature dephasing” of electrons has attracted a great deal of experimental [7–9] and theoretical atten- -173-