ABSTRACT
The field of spintronics has been developed, being triggered by the
discovery of giant magnetoresistance (GMR). Interaction between
fundamental physics and technological applications has brought
about novel concepts and phenomena in the field of spintronics
and in solid-state physics. Exchange coupling and the spin valve
appeared in the early stage of the development, being followed by
tunnel magnetoresistance (TMR), spin current, spin transfer torque,
the spin Hall effect, and the inverse spin Hall effect. Recently, various
types of torque acting on magnetization have been proposed. In
device applications, on the other hand, the GMR effect in spin valve
structures has been applied to magnetic sensors, and the TMR of
epitaxial ferromagnetic tunnel junctions (FTJs) has been applied to
magnetic (magnetoresistive) random access memories. Research of
further applications of such phenomena is still in progress in the
field of, for example, spin field-effect transistors (spin FETs). In this
chapter, we will explain the fundamental phenomena of GMR, TMR,
spin transfer torque, and their applications to devices and give a
brief introduction of the spin FET.
