Overview
During the last two decades, the world’s information is rapidly growing. The digital information is processed by electronic devices using semiconductor such as CMOS and stored in memory devices such as a hard disk drive (HDD). Spintronics (spin electronics) is an exciting research field that holds promise to build faster and more efficient devices to process and store the digital information, which is a new paradigm of electronics based on the spin degree of freedom of the electron. A key advantage of spins (magnetization is collective spins aligned in the one direction by the exchange interaction in magnets) is that the information is stored with the need for any power consumption, i.e., nonvolatility. We study static and dynamical properties of nano-scale magnets; to pursue efficient ultrafast control of the magnetization (Magnetic information are based on the orientation of the magnetization) and to generate spin current which is a flow of spin angular momentum. Ultimately, spin current could replace charge current for the information transfer and processing, allowing a development of a new class of nonvolatile electronics and low energy dissipation devices.
Spintronics
Spintronics (Spin electronics) is a new paradigm of electronics based on
the spin degree of freedom of the electron. One of the largest success
of this field lies in the discovery of the giant magnetoresistance (GMR)
in the late 1980s. The GMR effect increses a sensitivity of the conversion
between a magnetic field and an electric signal, allowing an increasing
in data storage density of HDD. In 2007, the Nobel prize has been awarded to Albert Fert and Peter Grunberg for
the discovery of this phenomena.
Magnetoresistive Random Access Memory (MRAM) is of great interest, as it potentially combines the high speed of SRAM,
density of DRAM, and the nonvolatile storage of Flash memory. The method
of reading data is accomplished by measuring the electrical resistance
of the memory cell which is comprised of magnetic tunnel junction. Data
is written to the memory cell by using a magnetic field. Recently, a new
technique, spin transfer torque, uses the writing method for STT-MRAM, which is an elegant and efficient way that relies on the spin-angular
momentum transfer from spin current to the magnetization. The STT-MRAM
has the advantage of lower power consumption and better scalability over
conventional MRAM.
Spin Current
Spin current is a flow of spin angular momentum without charge current. Taking advantage of the fact that electrons, magnons, photons and phonons have and intrinsic anular momentum offers a good opportunity to study their spin transport properties as well as to purse a wide range of applications, from HDD and MRAM to foward-looking spin-logic gates and spin-based quantum computing.
Beyond CMOS
Sooner or later, fundamental limination destine CMOS scaling to a conclusion. It is now apparent that improving the energy eficiency of computing is a challenge. Spintronic functions provide a complementary option to electronics. The added functionality includes nonvolatility and several new logic gates. This will make possible a new paradigm in computing, allowing circuits with no standby power dissipation, improved speed and better density and scaling.