Open Science Journal of Modern Physics 2015; 2(5): 55-64 Published online August 10, 2015 (http://www.openscienceonline.com/journal/osjmp) Quantum Spin Transport Characteristics in Graphene Field Effect Transistor Ahmed S. Abdelrazek 1 , Mohamed M. El-banna 2 , Adel H. Phillips 2, * 1 Faculty of Engineering, Kafr-Elsheikh University, Kafr-Elsheikh, Egypt 2 Faculty of Engineering, Ain-Shams University, Cairo, Egypt Email address ahmedagor2015@gmail.com (A. S. Abdelrazek), mm.elbanna@gmail.com (M. M. El-banna), adel.phillips@gmail.com (A. H. Phillips) To cite this article Ahmed S. Abdelrazek, Mohamed M. El-banna, Adel H. Phillips. Quantum Spin Transport Characteristics in Graphene Field Effect Transistor. Open Science Journal of Modern Physics. Vol. 2, No. 5, 2015, pp. 55-64. Abstract The spin dependent conductance of graphene field effect transistor is investigated in the present paper. Graphene field effect transistor is modeled as: ferromagnetic grapheme / superconducting graphene junction with Schottky barrier of δ-type at the interface of the junction. The conductance is deduced by using Landuar-Buttiker equation and the corresponding spin dependent Andreev reflection and the normal reflection coefficients are deduced by solving Dirac-Bogoliubov-deGennes equation in one dimension. The spin polarization transport is conducted under the effect of photon of an induced ac-field and magnetic field. Numerical calculations are performed for conductance for both parallel and antiparallel spin alignments and the corresponding spin polarization and giant magnetoresistance are also calculated. In our calculations we consider two different superconducting layers. Results show that the spin-dependent specular Andreev reflection in the present studied junction plays an important role for designing such nanodevice. Also, the Schottky barrier between the ferromagnetic graphene and superconductor graphene regions might be responsible for the conductance dip for both parallel and antiparallel spin alignments. The present paper is very important for spin filter, superconducting qubits needed for quantum information processing at low temperatures and also it might be used as THz oscillator. Keywords Spintronics, Ferromagnetic Graphene, Superconducting Graphene, Schottky Barrier, Specular Andreev Reflection, Ac-field, Magnetic Field 1. Introduction Nanotechnology can be understood as a technology of design, fabrication and applications of nanomaterials. In recent years, with the rapid research development of electronic devices and device miniaturization, nanometer sized electronic devices are in high demand for high performance, small power consumption and fast functionality. Spintronics aims to utilize the spin degree freedom of electrons for new forms of information storage and logic devices [1,2]. Recently, there has been great interest in spin logic devices [3.4] for high-speed, low-power operation, and spin transistors [5,6] for reconfigurable logic. For this purpose, a major challenge is developing a suitable spin transport channel with long spin lifetime and long- distance spin propagation. Recently, there has been much investment in the field of spintronics motivated by the tremendous potential for technological applications. Low- dimensional structures such as grapheme [7], nanowires [8], carbon nanotubes [9], quantum dots [6], silicene [10] are expected to lead to useful spintronic applications, possibly leading to the production of extremely efficient magnetic sensors, high-capacity memory storage, and non-volatile computer memories [1, 2]. Graphene was first discovered in 2004 by Novoselov et al. [11]. Graphene is a single atomic layer with a thickness of only 0.34 nm of sp 2 hybridized carbon atoms covalently bonded to three other atoms arranged in a honeycomb lattice [11-17]. Graphene's unique structural, mechanical, and electrical properties and high carrier mobility makes it one of the most important topics in materials science today [18-24]. Graphene has unique properties with tremendous potential applications, such as chemical sensors [25,26], nanoelectronic devices [27], hydrogen storage systems [28], or polymer nanocomposites [29]. Graphene [11, 30], the