Fondamental and applied research in the field of magnetism and magneto-electronics has lead to significant progress in the understanding of electronic interactions in solid states materials, and to numerous technological advances that we (as customers) are enjoying through faster computers, higher capacity hard drive, reduced size computer components...etc.  The intense research activity in condensed matter field has made the computer industry the fastest-growing, most vibrant in existence.

PRINCIPLE
Conventional electronic circuits use and control the flow of electrons. But electrons not only flow; they also spin about their own axis. This intrinsic angular momentum makes electrons act like tiny bar magnets that align either parallel (spin-up) or anti-parallel (spin- down)with respect to the direction of a local magnetic field. Furthermore, it turns out that ferromagnetic
materials, like cobalt, are able to spin-polarize a flow of electrons. In these
materials, the flow of spin-up electrons is favored via spin-dependent
scattering process: spin-down electrons experience more collisions.
Thus, the spin offers an additional degree of freedom that can be used
in electronics, in a field known as spintronics.

In 1988, the first spintronic device was synthesized by two European research groups [Phys. Rev. Lett.61, 2472-2475 (1988)]. The device is composed of two magnetic layers sandwiching a non magnetic metal. Each layer is only few nanometers thick. A large decrease of the resistance was observed when the relative magnetization alignment changes from parallel to antiparallel when a magnetic field is applied. The effect originates from spin-dependent scattering in magnetic materials, and is known as Giant Magnetoresistance (GMR). An analogy can be found with optical filters, where two polarizers in a crossed configuration are used to block light and reduce the transmission. Similarly, when the magnetic layers are anti-aligned the flow of electric current is impeded. GMR technology is widely used in current magnetic storage media as magnetic field sensors, and has increased the capacity of hard disks by 100 in the last five years.

                                         

RECENT ADVANCES
Recently, it was found that a flow of spin-polarized electrons generated by a magnetic element may interact with the magnetization of another magnet, triggering either its precession or its reversal, via transfer of spin angular momentum between layers [J. Magn. Magn. Mater.159, L1 (1996)]. The effect, known as spin transfer, was observed in a trilayer structure where two thin magnetic layers are separated by a non magnetic metal [Phys. Rev. Lett.80, 4281 (1998); ibid 91, 067203 (2003)]. The prospect of manipulating magnetic elements without applying magnetic fields is expected to be the basis for future high density magnetic storage media.

IMPACT
Spintronics promise a wide variety of new devices, thus changing the perspective of information technology in the 21st century. In the present-day machines, Random Access Memory (RAM) for example are semi conductor based. The information that is stored via electron charges is lost when the power is cut off. This is not the case when the information is stored magnetically, since magnets tend to stay magnetized. The prospect of reversing the magnetization by employing a spin polarized current provides a powerful solution for designing magnetic RAM. Experts also predict that the use of spin polarized currents in microelectronics may enhance the functionality of devices, combining logic, storage and sensor applications. It may also help reduce power usage, and as a result improve the portability of compact devices (laptop, camcorders, etc.).