Electric Control of Exchange Bias Training

Voltage-controlled exchange bias training and tunability are introduced. Isothermal voltage pulses are used to reverse the antiferromagnetic order parameter of magnetoelectric Cr2O3, and thus continuously tune the exchange bias of an adjacent CoPd film. Voltage-controlled exchange bias training is initialized by tuning the antiferromagnetic interface into a nonequilibrium state incommensurate with the underlying bulk. Interpretation of these hitherto unreported effects contributes to new understanding in electrically controlled magnetis

NF00-425 Resistance Management for European Corn Borer and Bt Transgenic Corn: Refuge Design and Placement (Revised October 2002)

One of the key issues surrounding the use of Bt transgenic corn hybrids is resistance management. These corn hybrids have been engineered to produce a version of the insecticidal protein from the naturally occurring soil bacterium, Bacillus thuringiensis (Bt), that is toxic to European corn borers and a few other insects. This NebFact discusses the important principles of resistance management for European corn borer and Bt corn and refuge considerations

HALL BAR DEVICE FOR MEMORY AND LOGIC APPLICATIONS

A hall bar device for a memory or logic application can include a gate electrode, a boron-doped chromia layer on the gate electrode; and a hall bar structure with four legs on the boron-doped chromia layer. For a memory application, the hall bar device can be written to by applying a pulse voltage across the gate electrode and one leg of the hall bar structure in the absence of an applied magnetic field; and can be read from by measuring a voltage across the one leg of the hall bar structure and its opposite leg

Voltage controlled magnetism in Cr2O3 based all-thin-film systems

Voltage-control of exchange biases through active selection of distinct domain states of the magnetoelectric and antiferromagnetic pinning layer is demonstrated for Cr2O3/CoPd heterostructures. Progress and obstacles towards an isothermal switching of exchange bias are discussed. An alternative approach avoiding exchange bias for voltage-controlled memory exploits boundary magnetization at the surface of Cr2O3 as voltage-controlled state variable. We demonstrate readout and switching of boundary magnetization in ultra-thin Cr2O3/Pt Hall bar devices where reversal of boundary magnetization is achieved via magnetoelectric annealing with simultaneously applied ±0.5 V and 400 mT electric and magnetic fields

The spin polarization of palladium on magneto-electric Cr\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e

While induced spin polarization of a palladium (Pd) overlayer on antiferromagnetic and magneto-electric Cr2O3(0001) is possible because of the boundary polarization at the Cr2O3(0001), in the single domain state, the Pd thin film appears to be ferromagnetic on its own, likely as a result of strain. In the conduction band, we find the experimental evidence of ferromagnetic spin polarized in Pd thin films on a Cr2O3(0001) single crystal, especially in the thin limit, Pd thickness of around 1–4 nm. Indeed there is significant spin polarization in 10 Å thick Pd films on Cr2O3(0001) at 310 K, i.e. above the Néel temperature of bulk Cr2O3. While Cr2O3(0001) has surface moments that tend to align along the surface normal, for Pd on Cr2O3, the spin polarization contains an in-plane component. Strain in the Pd adlayer on Cr2O3(0001) appears correlated to the spin polarization measured in spin polarized inverse photoemission spectroscopy. Further evidence for magnetization of Pd on Cr2O3 is provided by measurement of the exchange bias fields in Cr2O3/Pd(buffer)/[Co/Pd]n exchange bias systems. The magnitude of the exchange bias field is, over a wide temperature range, virtually unaffected by the Pd thickness variation between 1 and 2 nm

Dielectric properties of thin Cr2O3 films grown on elemental and oxide metallic substrates

In an attempt to optimize leakage characteristics of α-Cr2O3 thin films, its dielectric properties were investigated at local and macroscopic scale. The films were grown on Pd(111), Pt(111), and V2O3 (0001), supported on Al2O3 substrate. The local conductivity was measured by conductive atomic force microscopy mapping of Cr2O3 surfaces, which revealed the nature of defects that formed conducting paths with the bottom Pd or Pt layer. A strong correlation was found between these electrical defects and the grain boundaries revealed in the corresponding topographic scans. In comparison, the Cr2O3 film on V2O3 exhibited no leakage paths at similar tip bias value. Electrical resistance measurements through e-beam patterned top electrodes confirmed the resistivity mismatch between the films grown on different electrodes. The x-ray analysis attributes this difference to the twin free Cr2O3 growth on V2O3 seeding

Field Worker Exposure to Selected Insecticides Applied to Com Via Center-Pivot Irrigation

Field workerswere monitored for dermal and respiratory exposure to chlorpyrifos (with and without crop oil), carbaryl, and permethrin at reentry intervals of 2, 4, 8, 24, and 48 h after application. Insecticides were applied to R3 stage corn through an overhead center-pivot irrigation system. Dermal exposure was measured by analyzing 18 gauze pads attached to the clothing of workers to represent human body regions. Hand exposure was determined using cotton gloves. Respiratory exposure was determined using portable air samplers equipped with polyurethane foam plugs to trap ambient insecticide residues. Gas liquid chromatography was used to quantify residues of chlorpyrifos and permethrin in gauze pads, gloves, and foam plugs. Carbaryl residues in pads, gloves, and foam plugs were analyzed using high-performance liquid chromatography. Highest dermal and respiratory exposures were found at the 2-h reentry interval. Exposures decreased as reentry interval increased. Dermal exposure was primarily confined to the hands. Residues detected by air samplers ranged from 0 to 0.03 μg/liter. Based on the estimated percentages of acute toxic dose (all \u3c0.00038%), the risk of acute toxicity to workers at the intervals studied was low

Post deposition interfacial N\'eel temperature tuning in magnetoelectric B:Cr2O3

Boron (B) alloying transforms the magnetoelectric antiferromagnet Cr2O3 into a multifunctional single-phase material which enables electric field driven {\pi}/2 rotation of the N\'eel vector. Nonvolatile, voltage-controlled N\'eel vector rotation is a much-desired material property in the context of antiferromagnetic spintronics enabling ultra-low power, ultra-fast, nonvolatile memory, and logic device applications. N\'eel vector rotation is detected with the help of heavy metal (Pt) Hall-bars in proximity of pulsed laser deposited B:Cr2O3 films. To facilitate operation of B:Cr2O3-based devices in CMOS environments, the N\'eel temperature, TN, of the functional film must be tunable to values significantly above room temperature. Cold neutron depth profiling and x-ray photoemission spectroscopy depth profiling reveal thermally activated B-accumulation at the B:Cr2O3/ vacuum interface in thin films deposited on Al2O3 substrates. We attribute the B-enrichment to surface segregation. Magnetotransport data confirm B-accumulation at the interface within a layer of about 50 nm thick where the device properties reside. Here TN enhances from 334 K prior to annealing, to 477 K after annealing for several hours. Scaling analysis determines TN as a function of the annealing temperature. Stability of post-annealing device properties is evident from reproducible N\'eel vector rotation at 370 K performed over the course of weeks