A5084041247- Magnetic properties of thin films
- Ferroelectric and Negative Capacitance Devices
- Magnetic and transport properties of perovskites and related materials
- Semiconductor materials and devices
- Advanced Condensed Matter Physics
- Multiferroics and related materials
- Physics of Superconductivity and Magnetism
- Magnetic Properties and Applications
- Neural Networks and Reservoir Computing
- ZnO doping and properties
- Magneto-Optical Properties and Applications
- Advanced Memory and Neural Computing
- Advanced Data Storage Technologies
- Quantum and electron transport phenomena
- Characterization and Applications of Magnetic Nanoparticles
- Magnetic Properties and Synthesis of Ferrites
- Electronic and Structural Properties of Oxides
- Theoretical and Computational Physics
University of California, Berkeley
2012-2015
Stanford University
2015
Lawrence Berkeley National Laboratory
2012
Spin-transfer-torque magnetic random access memory (STT-MRAM) is the most promising emerging non-volatile embedded memory. For applications, a wide range of operating temperatures required, for example -40 °C to +150 automotive applications. This presents challenge STT-MRAM, because anisotropy responsible data retention decreases rapidly with temperature. In order compensate loss thermal stability at high temperature, devices must be increased. in turn leads larger write currents lower...
Abstract Perpendicular magnetic anisotropy (PMA) ferromagnetic CoFeB with dual MgO interfaces is an attractive material system for realizing memory applications that require highly efficient, high speed current-induced switching. Using this structure, a sub-nanometer layer has the potential to simultaneously exhibit switching in accordance conservation of spin angular momentum, and thermal stability owing enhanced interfacial PMA arises from two CoFeB-MgO interfaces. However, difficulty...
We present recent advances in writing speed of pSTT_MRAM which demonstrate its potential as a candidate for replacement LCC cache advanced technology nodes well applications where non-volatility may be needed. In this paper we explore the feasibility sub-ns switching devices and their characterization using comprehensive time resolved electrical measurement reversal mechanism. show that mechanism can described simple nucleation followed by propagation model characterized statistically....
We present for the first time STT-MRAM devices with ultra low operating voltage and power compatible next generation 0x node logic voltages. By engineering tunnel barrier improving efficiency of we report a record writing 0.17V 1ppm error rate, which has been achieved 20ns write operation using current only 35uA. further demonstrate rates below 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> at 0.25V 50uA 10ns pulses on same 30nm...
Last-Level-Cache applications at 0X technology nodes require devices switching reliably in less than 10ns currents smaller 50uA, while preserving data retention up to 85°C. In this paper, we show that both low Gilbert damping and magnetic moment are the primary factors for efficient writing nanosecond time scales. We report comprehensive device-level measurements of using conventional free layer designs an optimized combines meets LLC requirements.
Scaling STT-MRAM cells beyond 1X technology nodes will require MTJ devices smaller than 30 nm. For such small sizes, process-induced damage becomes a primary factor of device performance. A robust method assessing magnetic properties sub-30 nm is thus needed. Here we report measurements the anisotropy field H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</sub> down to 20 using ST-FMR. We show that increases for decreasing sizes. The...
We demonstrate the stabilization of a ferrimagnetic ground state in epitaxial films PrCoO${}_{3}$ grown on SrTiO${}_{3}$ (001) substrates, stark contrast to paramagnetic behavior observed bulk. Heteroepitaxial strain is found induce long-range ordering Co ions, which we deduce be high-spin state. The ferromagnetic CoO${}_{6}$ array accompanied by Pr sublattice an antiparallel orientation Co. provides evidence for significant Co-Pr exchange likely facilitated presence
Epitaxial La2/3Sr1/3MnO3 films grown on LaAlO3 substrates of various orientations exhibit a range magnetoresistive properties, demonstrating the utility strain as an electronic tuning parameter for manganites. Large magnetoresistance over broad temperatures—highest (−64% at 50 kOe) lowest temperatures measured—is observed in coherently strained film (001) substrate. In addition to higher magnetoresistance, its reduced magnetization and conductance suggest stabilization more insulating ground...
We demonstrate distinct magnetic and resistive switching with junction magnetoresistance up to −6% in tunnel junctions a CuCr2O4 barrier. Junction is inversely related barrier thickness reveals maximum at finite applied bias that converges zero low temperatures for all thicknesses. The non-monotonic dependence attributed charge gap from the Fe3O4 electrode possible spin filtering spin-split conduction band of ferrimagnetic
Competing exchange interactions can give rise to varying degrees of frustration that manifest itself in noncollinear magnetic moment ordering or canonical geometric magnets with large ground-state degeneracies. Relieving this has the potential stabilize ground states inaccessible bulk. We demonstrate heteroepitaxial lattice distortions modify strength thin films frustrated ferrimagnet, CuCr${}_{2}$O${}_{4}$. The reduction CuCr${}_{2}$O${}_{4}$ through results greater collinear spin and an...
Nanocrystalline (NC) textured Mn0.5Zn0.6Fe1.9O4 (MZFO) films, grown at room temperature on both isostructural and non-isostructural substrates, show magnetization values significantly suppressed from epitaxial MZFO films. X-ray absorption spectroscopy x-ray magnetic circular dichroism measurements indicate larger ratios of Fe3+ to Fe2+ ions the tetrahedral sites in NC films compared The loops are shifted by 200−400 Oe low temperatures. No such effect is observed We hypothesize that presence...
Spin-Transfer-Torque Magnetic Random Access Memory (STT-MRAM) is emerging as a leading candidate for variety of embedded memory applications ranging from NVM to working and last level cache. In this paper, we review recent breakthroughs that have brought perpendicular STT-MRAM the cusp mass production.
Spin Transfer Torque Magnetic Random Access Memories (STT-MRAM) are based on Tunnel Junctions (MTJs) made out of two ferromagnetic electrodes separated by a MgO tunnel barrier. Here we report experimental data the STT-induced dynamics SAF RL in perpendicularly magnetized STT-MRAM devices. We show evidence different dynamical modes depending properties. also develop an analytical model 3-layer macrospin model, which allows us to reproduce main feature and derive phase diagram dynamics....
Spin Transfer Torque Magnetic Random Access Memory (STT-MRAM) is the leading technology for next generation non-volatile embedded memories. In this presentation, we use Spin-Torque Ferromagnetic Resonance (ST-FMR) to measure anisotropy field of perpendicularly magnetized devices down 25 nm in size. We show that effective HK <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> , including demagnetizing field, exceeds 10 kOe at room...
Significant progresses have been made in recent years perpendicular spin torque transfer magnetic random access memory (pSTT-MRAM) technology development by many companies or organizations. Commercialization of pSTT-MRAM is more real today than ever the long history MRAM development. We recently reported fully functional chips and macros with sub-5ns writing speed based on 90nm 40nm node CMOS technologies [1,2]. These can be potentially used to replace current embedded non-volatile memories...
To consider STT-MRAM as an SRAM replacement, the reliability of MTJ devices has to be demonstrated. A comprehensive study degradation magnetic tunnel junction barrier under stress is presented in this paper. It found that breakdown mechanism such follows a consistent path soft (SBD) followed by hard (HBD). We discuss strategy improve write margin reducing resistance area product (RA) barrier. Finally, we link our single device studies similar endurance performed on fully functional chips.