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Key design parameters of 64 Mb STT-MRAM at 90-nm technology node are discussed. A design point was developed with adequate TMR for fast read operation, enough energy barrier for data retention and against read disturbs, a write voltage satisfying the long term reliability against dielectric breakdown and a write bit error rate below 10-9. A direct experimental method was developed to determine the data retention lifetime that avoids the discrepancy in the energy barrier values obtained with spin current- and field-driven switching measurements. Other parameters detrimental to write margins such as backhopping and the existence of a low breakdown population are discussed. At low bit-error regime, new phenomenon emerges, suggestive of a bifurcation of switching modes. The dependence of the bifurcated switching threshold on write pulse width, operating temperature, junction dimensions and external field were studied. These show bifurcated switching to be strongly influenced by thermal fluctuation related to the spatially inhomogeneous free layer magnetization. An external field along easy axis direction assisting switching was shown to be effective for significantly reducing the percentage of MTJs showing bifurcated switching. [ABSTRACT FROM AUTHOR]

Ozone (O3) concentrations in periurban areas in East Asia are sufficiently high to decrease crop yield. However, little is known about the genotypic differences in O3 sensitivity in winter wheat in relation to year of cultivar release. This paper reports genotypic variations in O3 sensitivity in 20 winter wheat cultivars released over the past 60 years in China highlighting O3-induced mechanisms. Wheat plants were exposed to elevated O3 (82 ppb O3, 7 h day−1) or charcoal-filtered air (<5 ppb O3) for 21 days in open top chambers. Responses to O3 were assessed by the levels of antioxidative activities, protein alteration, membrane lipid peroxidation, gas exchange, leaf chlorophyll, dark respiration and growth. We found that O3 significantly reduced foliar ascorbate (−14%) and soluble protein (−22%), but increased peroxidase activity (+46%) and malondialdehyde (+38%). Elevated O3 depressed light saturated net photosynthetic rate (−24%), stomatal conductance (−8%) and total chlorophyll (−11%), while stimulated dark respiration (+28%) and intercellular CO2 concentration (+39%). O3 also reduced overall plant growth, but to a greater extent in root (−32%) than in shoot (−17%) biomass. There was significant genotypic variation in potential sensitivity to O3 that did not correlate to observed O3 tolerance. Sensitivity to O3 in cultivars of winter wheat progressed with year of release and correlated with stomatal conductance and dark respiration in O3-exposed plants. O3-induced loss in photosynthetic rate was attributed primarily to impaired activity of mesophyll cells and loss of integrity of cellular membrane as evidenced by increased intercellular CO2 concentration and lipid peroxidation. Our findings demonstrated that higher sensitivity to O3 in the more recently released cultivars was induced by higher stomatal conductance, larger reduction in antioxidative capacity and lower levels of dark respiration leading to higher oxidative damage to proteins and integrity of cellular membranes. [ABSTRACT FROM AUTHOR]

We present a dynamic strain field mapping method based on synchrotron X-ray digital image correlation (XDIC). Synchrotron X-ray sources are advantageous for imaging with exceptional spatial and temporal resolutions, and X-ray speckles can be produced either from surface roughness or internal inhomogeneities. Combining speckled X-ray imaging with DIC allows one to map strain fields with high resolutions. Based on experiments on void growth in Al and deformation of a granular material during Kolsky bar/gas gun loading at the Advanced Photon Source beamline 32ID, we demonstrate the feasibility of dynamic XDIC. XDIC is particularly useful for dynamic, in-volume, measurements on opaque materials under high strain-rate, large, deformation. [ABSTRACT FROM AUTHOR]

Spin-transfer torque magnetic random access memory (STT-MRAM) is one of the most promising emerging non-volatile memory technologies. MRAM has so far been demonstrated with a unique combination of density, speed, and non-volatility in a single chip, however, without the capability to replace any single mainstream memory. In this paper, we demonstrate the basic physics of spin torque switching in 20 nm diameter magnetic tunnel junctions with perpendicular magnetic anisotropy materials. This deep scaling capability clearly indicates the STT MRAM device itself may be suitable for integration at much higher densities than previously proven. [ABSTRACT FROM AUTHOR]

Spin torque switching is investigated in perpendicular magnetic tunnel junctions using Ta|CoFeB|MgO free layers and a synthetic antiferromagnet reference layer. We show that the Ta|CoFeB interface makes a key contribution to the perpendicular anisotropy. The quasistatic phase diagram for switching under applied field and voltage is reported. Low switching voltages, Vc 50 ns=290 mV are obtained, in the range required for spin torque magnetic random access memory. Switching down to 1 ns is reported, with a rise in switching speed from increased overdrive that is eight times greater than for comparable in-plane devices, consistent with expectations from a single-domain model. [ABSTRACT FROM AUTHOR]

Schwannomas of the pancreas are rare tumors. We report a case of solitary schwannoma of the pancreas without von Recklinghausen disease. A 72-year-old man underwent routine abdominal ultrasound before cholecystectomy because of chronic cholecystitis and multiple gallstones, and ultrasound showed a small solitary tumor in the pancreas. Spiral computed tomography showed a 1.0-cm, well-defined homogeneous hypodense lesion with mild inhomogeneous enhancement and peripheral enhancement at the junction between the head and body of the pancreas. These computed tomographic findings are different from those in previous reports. [ABSTRACT FROM AUTHOR]

CoFeB-based magnetic tunnel junctions with perpendicular magnetic anisotropy are used as a model system for studies of size dependence in spin-torque-induced magnetic switching. For integrated solid-state memory applications, it is important to understand the magnetic and electrical characteristics of these magnetic tunnel junctions as they scale with tunnel junction size. Size-dependent magnetic anisotropy energy, switching voltage, apparent damping, and anisotropy field are systematically compared for devices with different materials and fabrication treatments. Results reveal the presence of sub-volume thermal fluctuation and reversal, with a characteristic length-scale of the order of approximately 40 nm, depending on the strength of the perpendicular magnetic anisotropy and exchange stiffness. To have the best spin-torque switching efficiency and best stability against thermal activation, it is desirable to optimize the perpendicular anisotropy strength with the junction size for intended use. It also is important to ensure strong exchange-stiffness across the magnetic thin film. These combine to give an exchange length that is comparable or larger than the lateral device size for efficient spin-torque switching. [ABSTRACT FROM AUTHOR]