Spintronics  


⊙ STO synchronization 

The effort on commercialization of single spin torque oscillator(STO) has reached threshold due to its low output power and wide line width. Recently, synchronization of STOs by fabricating in arrays has been studied to breakthrough these limitations.

AC magnetic field derives injection locking of STOs. Electrical synchronization can be achieved by AC currents from STOs in array structure, whereas synchronization by magnetic coupling can be occurred from dipole magnetic interaction.

In this laboratory, we calculate physical parameters in a device level as well as synchronization of STO array by integrating with circuit theory, especially to resolve output power and line width problems.

We also deal with various STO devices such as GMR valve, MTJ pillar, and spin Hall oscillator.



⊙ MTJ Macroscopic simulation

 Considerable interests in spintronic devices, especially spin-transfer torque magnetic random access memory (STT-MRAM) and spin torque nano-oscillators (STNOs) have brought remarkable developments.

For the numerical study of spin transfer effects inside the core part, called magnetic tunnel junction (MTJ), we analyze nanoscale system using nonequilibrium Green’s function (NEGF), which is known as the most powerful method to describe submicron devices.

Landau-Lifshitz-Gilbert (LLG) equation determines dynamics of free magnetic layer. Combining NEGF formalism and LLG equation, self-consistent calculation describes consecutive change of magnetization vector.