Spintronics Research
Our laboratory also devotes to the research of spintronics, which exploits the intrinsic magnetic property of electron called spin, adding a new degree of freedom to conventional electronics. Since the discovery of the giant magneto-resistance (GMR) effect in the late 80's, Spintronics has been paving the path for advanced new technologies with the unique advantage against semiconductor devices that they are nonvolatile. Efficient control of the magnetic states of spintronics devices by spin-orbit torques, Dzyaloshinskii–Moriya interaction, voltage controlled magnetic anisotropy, exchange bias from antiferromagnets and other effects arising at the interface between magnetic and non-magnetic materials are main focus of our research.
Magnetoresistive Random Access Memory (MRAM)
Magnetoresistive Random Access Memory (MRAM) is a type of non-volatile memory technology that uses the magnetic orientation of ferromagnetic materials to store binary data. Unlike traditional memory technologies, MRAM does not rely on electrical charges, offering fast read and write speeds, low power consumption, and high endurance. The data in MRAM is retained even when power is turned off, making it suitable for applications requiring non-volatile memory. MRAM's unique combination of speed, endurance, and non-volatility positions it as a promising technology for various applications, including embedded systems, IoT devices, and aerospace technology.
Our laboratory is dedicated to cultivating talent in the field of MRAM and maintaining close connections with the industry. Our group is the most important training and education hub for MRAM talents in Taiwan.
Publications
First BEOL-compatible, 10 ns-fast, and Durable 55 nm Top-pSOT-MRAM with High TMR (>130%)
Spin-orbit Torques
The conversion of charge current into spin current based on the Spin Hall and Rashba effects provides a new way of spin injection and manipulation in novel spintronic architectures. The realization of a large conversion efficiency between the charge and spin currents is a crucial issue for its applications. By applying pulses of electrical current, it has been demonstrated that the generated spin–orbit torque (SOT) serves as an effective means to manipulate the magnetization of the ferromagnetic layer.
Publications
Fig. 1. Schematic of MOKE setup for the measurement of switching and pulsed current/voltage spin-orbit torque switching
Antiferromagnetic Spintronics
Antiferromagnet (AFM) spintronics has currently been an emergent research field of wide scientific interests because of several uniqueness of AFM as magnetic robustness, absence of stray field, and ultrafast dynamics. It makes AFM family transit from a passive role in the conventional spintronics to an active page in the advanced applications. Recently it has been demonstrated that the FM/AFM bilayer exhibits field-free SOT switching, where the AFM layer plays a dual role as the in-plane pinning layer and the source of spin current.
Publications
Fig. 3. The FM magnetization and interfacial spins between the AFM and FM layers initially configured in antiparallel directions and the initial exchange bias from the shifted M–H curve.
Multilevel and Neuromorphic spin devices
Multilevel storage has not only been developed in the commercialized multilevel-cell Flash, but also been demonstrated in most of the nonvolatile memories. For multilevel-cell MRAM, the multilevel magneto-resistive states in magnetic tunnel junctions are created by changing magnetic domain configurations of the free layer. Magnetic multilevels states have found an opportunity for non-conventional computing such as Neuromorphic computing since they can mimic the behavior of synapses, offering the non-volatility and low power consumption of spintronic devices, making spintronics research a major contributor for future technologies.
Publications
Fig. 4. Multilevel states on the Co/Pt multilayers driven by spin–orbit torque and distributions of the corresponding final magnetization states of each pulse condition.