EAGER-Generation of Perpendicularly Polarized Spin Current from the Spin-Orbit Effects in Ferromagnetic Thin Film Structures for Memory Applications

University Of Denver, Denver CO

Investigators

Abstract

To accommodate the ever-increasing demand of computational power, there has been a great effort in searching for new types of memories that are fast and energy-efficient. Magnetic random access memory, which uses magnetism to store information and electricity to read/write information, is a potential candidate as the new generation of memory because magnetism is intrinsically non-volatile and switches fast. The main technical challenge is to reduce the amount of energy it takes to switch the magnetization in the writing process of the magnetic random access memory. This project aims to explore an efficient way to switch the magnetization by using a spin current, i.e. a flow of electron spins, with a specially engineered spin orientation. This work will provide transformative information on how to generate perpendicular spins from magnetic structures, which will significantly lower the power consumption in magnetic random access memories with perpendicular magnetizations. The outcome from this research will lead to a significant advance in data storage and information technologies. The spin-orbit effects have been demonstrated to be a promising way to convert an electric current into a spin current that can efficiently switch a magnetization. However, thus far the spin currents generated by the spin-orbit effects are constrained by thin film geometries and therefore are only polarized in-plane. It is inefficient to use an in-plane polarized spin current to switch a perpendicular magnetization, which is technically attractive in the application of memories due to their scalability and thermal stability. In this proposal, the investigator plan to explore the generation of a perpendicularly polarized spin current using the spin-orbit effects in ferromagnetic structures, which is based on the hypothesis that the ferromagnetism provides an additional control on the spin orientation. Two complementary structures will be investigated: the spin filtering, where the spin polarization is aligned with the magnetization, and spin rotation, where the spin polarization is rotated about the magnetization. This project leverages on unique expertise in detecting the spin torque on magnetization using the sensitive magneto-optic-Kerr-effect magnetometry and ferromagnetic resonance-based magnetometry. The specific tasks in the project are (1) quantifying the efficiency to generate perpendicularly polarized spin current in the two ferromagnetic structures and (2) designing efficient device for switching magnetization with a fast switching time. This study will also provide important insights in the comprehensive spin-orbit effects from magnetic structures.