Our nonvolatile spintronics team focuses on research on magnetic materials, devices, and architectures for nonvolatile memory and logic. The term nonvolatile refers to devices and circuits which do not require the continuous application of a voltage (hence power) to retain their information. Hence, these devices enable electronic systems with extremely low standby power, thereby enhancing their overall power efficiency. They also allow for integration of memory and logic functions at a more fundamental level. By eliminating the need to transfer data back and forth from/to power-hungry and slow external nonvolatile memories, they contribute to improving the system speed, allowing for instant on/off capability. Finally, by enhancing energy efficiency and reducing leakage and standby power consumption, these nonvolatile spintronic solutions allow for greatly improved scaling behavior of (CMOS or beyond-CMOS) logic architectures. Our activities in this area can broadly be divided into work on magnetic random access memory (MRAM) and nonvolatile magnetic logic (NVL).
We are investigating various aspects of this area of research, ranging from materials development, theoretical modeling and simulations, to advanced measurements, and development of various memory and logic devices and circuits. We have extensive collaborations and partnerships with leading experts in academia and industry. Our efforts in this area are supported by DARPA, and by the TANMS and WIN centers at UCLA.
For more information, please contact Dr. Pedram Khalili – pedramk (at) ucla (dot) edu.
I. Magnetic Random Access Memory (MRAM)
|Figure 1. Images of MeRAM devices developed by our team (top); and measured switching probability as a function of write voltage for a MeRAM bit (bottom). For details see “Voltage-Induced Switching of Nanoscale Magnetic Tunnel Junctions“, Technical Digest of the IEEE International Electron Devices Meeting (IEDM 2012), San Francisco, California, pp. 29.5.1-29.5.4, December 2012, and “Voltage-controlled MRAM: Status, challenges and prospects“, EE Times, February 25, 2013.|
Magnetoresistive Random Access Memory (MRAM) is currently of great interest, as it potentially combines (and exceeds) the high speed of SRAM, density of DRAM, and the nonvolatile storage of Flash memory in a single scalable memory technology with excellent endurance and low energy. Our team has been leading research in the development of spin transfer torque memory (STT-MRAM) using MgO-based magnetic tunnel junction (MTJ) devices. More recently, we are also working actively on a new type of electric-field-controlled MRAM which we refer to as magnetoelectric random access memory, or MeRAM. The use of electric fields (i.e. voltages) rather than currents allows for 10-100x lower power dissipation, higher density, and better scalability. Our efforts cover the full range of activities ranging from material and MTJ stack development to testing and characterization, as well as micromagnetic modeling.
II. Nonvolatile Logic Circuits (NVL)
Figure 2. Device structure and oscillation spectra of ultralow-current spin torque nano-oscillators (STNOs) developed by our team. For details see “Ultralow-current-density and bias-field-free spin-transfer nano-oscillator“, Scientific Reports, Vol. 3, pp. 1426/1-5, March 2013, and “High-Power Coherent Microwave Emission from Magnetic Tunnel Junction Nano-Oscillators with Perpendicular Anisotropy”, ACS Nano, Vol. 6, No. 7, pp. 6115-6121, 2012.
Our team is also developing nonvolatile logic for ultralow-power electronic systems of the future. Our approach here is two-fold. On the one hand we work on combining our ultralow-power and fast magnetic memory devices with existing volatile CMOS logic, in collaboration with leading circuit designers at UCLA, in order to create nonvolatile circuits with no standby power dissipation, improved speed, and better density and scaling. Our second approach is to create all-spintronic logic based on spin waves in magnetic nanostructures, which we refer to as nonvolatile magnonic logic. Here we work on combining spin wave logic devices with novel non-volatile elements, to create an all-encompassing new approach to computational logic. This will make possible a new paradigm in computing, extending the reach of nonvolatile electronics from memory to logic and computing applications, allowing for zero standby power and instant-on computation.
IN THE NEWS
- Read our article in EE Times on voltage-controlled Magnetoelectric RAM (MeRAM): P. Khalili and K. Wang, “Voltage-controlled MRAM: Status, challenges and prospects“, EE Times, February 25, 2013.
- Research team develops new compact and energy-efficient nanoscale microwave oscillators News report on our paper in Scientific Reports, 3, 1426 (2013)
- UCLA engineers develop new energy-efficient computer memory using magnetic materials News report on our paper at the IEDM 2012 conference
- UCLA-led research team develops world’s most powerful nanoscale microwave oscillators News report on our paper in ACS Nano, 6, 6115 (2012),
- Magnetic Logic Attracts Money – IEEE Spectrum Report on our DARPA Nonvolatile Logic program
- Z.M. Zeng, G. Finocchio, B. Zhang, P. Khalili Amiri, J.A. Katine, I.N. Krivorotov, Y. Huai, J. Langer, B. Azzerboni, K.L. Wang, H.W. Jiang, “Ultralow-current-density and bias-field-free spin-transfer nano-oscillator“, Scientific Reports, Vol. 3, pp. 1426/1-5, March 2013.
- K.L. Wang, J.G. Alzate, P. Khalili Amiri, “Low-power non-volatile spintronic memory: STT-RAM and beyond“, Journal of Physics D: Applied Physics, Vol. 46, No. 7, pp. 074003/1-10, February 2013. (Invited Review)
- P. Khalili Amiri, P. Upadhyaya, J.G. Alzate, K.L. Wang, “Electric-field-induced thermally assisted switching of monodomain magnetic bits”, Journal of Applied Physics, Vol. 113, No. 1, pp. 013912/1-5, January 2013.
- J.G. Alzate, P. Khalili Amiri, P. Upadhyaya, S.S. Cherepov, J. Zhu, M. Lewis, R. Dorrance, J.A. Katine, J. Langer, K. Galatsis, D. Markovic, I. Krivorotov, K.L. Wang, “Voltage-Induced Switching of Nanoscale Magnetic Tunnel Junctions“, Technical Digest of the IEEE International Electron Devices Meeting (IEDM 2012), San Francisco, California, pp. 29.5.1-29.5.4, December 2012.
- Z.M. Zeng, P. Khalili Amiri, I. Krivorotov, H. Zhao, G. Finocchio, J.-P. Wang, J.A. Katine, Y. Huai, J. Langer, K. Galatsis, K.L. Wang, H.W. Jiang, “High-Power Coherent Microwave Emission from Magnetic Tunnel Junction Nano-Oscillators with Perpendicular Anisotropy”, ACS Nano, Vol. 6, No. 7, pp. 6115-6121, 2012.
- J. Zhu, J.A. Katine, G.E. Rowlands, Y.-J. Chen, Z. Duan, J.G. Alzate, P. Upadhyaya, J. Langer, P.K. Amiri, K.L. Wang, I.N. Krivorotov, “Voltage-Induced Ferromagnetic Resonance in Magnetic Tunnel Junctions“, Physical Review Letters, Vol. 108, No. 19, pp. 197203/1-5, 2012.