INTRODUCTION

Spintronics studies the use of spin freedom of electrons. It originated from the giant magnetic resistance (GMR) effect found by Fert and Gruenberg, respectively, in 1988. This discovery produced highly sensitive magnetic sensors, used in the read-out head of the magnetic hard disk. Just after 9 years as the GMR was discovered, in November 1997 IBM Co. declared that they fabricated the commercial read-out head of the magnetic hard disk. This product accomplished an enterprise of several billions of US dollars. The spin electronic devices under study include magnetic random access memory (MRAM), spin field effect transistor (FET), spin-polarized laser, etc. These devices depend on their ability to control spin in the solids and they can be used to decrease the power consumption, to overcome the velocity limit connected with the charge electrons, and in the quantum information treatment and quantum computation in future…