UC Irvine

Spin transfer torque is generated by the transfer of angular momentum from spin polarized electrons to a ferromagnet. This spin transfer torque provides an efficient way to manipulate the dynamic motion of the magnetization of a nanomagnet, and can be strong enough to induce magnetization switching and steady-state precession. This field of study draws enormous attention not only because spin transfer torque is essential in understanding fundamental physical phenomena, but also it makes the building block for future applications such as spin torque oscillators, magnetic random access memory. We have developed several new techniques to characterize such dynamics in nanoscale magnetic tunnel junctions. In this thesis we will first introduce a effect methods to characterize important material parameters in nano-scale magnetic tunnel junctions(MTJs): spin-torque ferromagnetic resonance. This methods combing with micromagnetic modeling allows us to determine the magnetic anisotropy, Gilbert damping, exchange stiffness and shape distortion and damages. We will also demonstrate a single-shot electrical technique to capture the magnetic dynamics during the spin torque switching of a magnetic tunnel junction in real time. We also discuss measurement of switching probability of magnetic tunnel junctions by applying electric pulses.