Contents lists available at ScienceDirect Physica E: Low-dimensional Systems and Nanostructures journal homepage: www.elsevier.com/locate/physe Coherent spin transport properties of ferromagnetic graphene superlattice unit cell Mina D. Asham a,* , Adel H. Phillips b a Faculty of Engineering, Benha University, Benha, Egypt b Faculty of Engineering, Ain-Shams University, Cairo, Egypt ARTICLE INFO Keywords: Spin polarization Normal and ferromagnetic graphene superlattice Ferromagnetic insulator EuO Giant magneto-resistance ac-field with different frequencies ABSTRACT The Aim of this paper is to study the properties of spin transport for ferromagnetic graphene superlattice unit cell junction taking into account the induced ac-field at different frequencies. Transfer matrix method is used for both spin alignments to calculate the conductance in terms of which spin polarization and giant magneto- resistance are also expressed. The results show that an oscillatory behavior is strongly exhibited by the three calculated quantities. These oscillations could be explained by the mutual effect between the magnetic field of the ferromagnetic insulator EuO, which causes spin filtering, and the induced photon energy of applied ac-field. The present research might have a scientific potential in the design and understanding of graphene superlattice based spin filters by optimizing the different parameters studied in this paper. 1. Introduction Spintronics is a new branch of electronics in which electron spin, in addition to charge, is manipulated to yield a desired electronic out- come. All spintronic devices act according to the simple scheme: (1) information is stored (written) into spins as a particular spin orientation (up or down), (2) the spins, being attached to mobile electrons, carry the information along a wire, and (3) the information is read at a terminal [1–4]. Spin orientation of conduction electrons survives for a relatively long time (nanoseconds, compared to tens of femto-seconds during which electron momentum and energy decay), which makes spintronic devices particularly attractive for memory storage and magnetic sensors applications, and, potentially for quantum computing where electron spin would represent a bit (called qubit) of information [5–8]. Two-dimensional (2D) nanomaterials are one of the most attractive research topics due to their outstanding potential applications in many fields, such as flexible electronics [9], sensing [10], and optics [11], as a result of their desirable physical and structural properties [12–15]. Among the 2D materials, graphene is outstanding as it has the highest charge carrier mobility [16], but fails to act as a semiconductor due to a lack of band-gap in its electronic structure [17]. Graphene is a monoatomic layer of carbon, making it a truly two-dimensional mate- rial [18,19]. It possesses special electronic, mechanical, optical and thermal properties making it a promising candidate for many applications in nanoelectronics and spintronics [20–27]. Interesting composite systems comprising graphene alongside other nano-struc- tures have been studied for better understanding of their physical roles. Some of these studies exhibit the behavior of graphene under the ex- posure to electromagnetic fields through the observed stimulated sur- face plasmons [28–31]. Graphene superlattices (SLs) represent novel class of electronic materials that can be used to modify the band structure of graphene. This fact offers the possibility of controlling and manipulating the corresponding electronic properties, opening stimu- lating perspectives for the development of electronic devices with new functionality. Such control and manipulation may be achieved elec- tronically by applying gate voltages [32]. When studying the electronic properties of infinite graphene SLs, the dispersion relation and related quantities, as the group velocity and density of states (DOS), are con- cepts of fundamental importance. Due to this, their properties have been investigated by different authors. These investigations revealed that SL in graphene generates extra Dirac points or cones [32–36] for which the group velocity shows an anisotropic behavior [33,37], leading to the possibility of collimation [38]. It was also shown that the density of states of infinite graphene SLs [32,33,35] displays oscilla- tions as a function of the energy and exhibits peaks between the Dirac points, which are reflected in the conductivity of the system. The purpose of the present paper is to investigate the spin polar- ization transport characteristics of single layer ferromagnetic graphene superlattice, considering for simplicity a single unit cell, under the https://doi.org/10.1016/j.physe.2019.05.003 Received 3 January 2019; Received in revised form 21 April 2019; Accepted 5 May 2019 * Corresponding author. E-mail addresses: mina.muawwad@bhit.bu.edu.eg (M.D. Asham), adel_phillips@eng.asu.edu.eg (A.H. Phillips). Physica E: Low-dimensional Systems and Nanostructures 113 (2019) 97–102 Available online 06 May 2019 1386-9477/ © 2019 Elsevier B.V. All rights reserved. T