Nano-scale control of magnetoelectronics for device applications

Novel high performance magneto-electronic devices suitable for the next-generation information technology require understanding of the basic physics of non-equilibrium coupling between current and magnetization. In the project, we have studied, tunnel magnetoresistance (TMR), current induced magnetization reversal (CIMR), effects of spin current, magneto-transport in nano-scale magnets and semiconductors, and magnetic transistors. The theoretical study of TMR indicates that TMR is strongly affected by disorder. Experiments showed that ferrimagnetically coupled trilayers (SyFI) are useful for both TMR junctions and magnetic elements in CPP-MR junctions for CIMR. Especially, the critical current density has been reduced to 62 11 0 A / cm − × by using SyFI with a Ru layer. It is shown that the pumping of spins slows down the precession, resulting an enhancement of Gilbert damping factor, and that the role of spin-torque and mixing conductance are important for the experimental analysis of CIMR. Spin accumulation in FM/NM/FM has been confirmed experimentally. Theoretical prediction of the spin accumulation, vanishing of the spin Hall current in Rashba split 2DEG have been presented. Large MR has been observed in resonant tunnel diodes, one-dimensional III-VI magnetic semiconductors as well as in tunnel magnetic transistors. The results may contribute the progress in the magneto-electronics for device applications.