From the zero-field metal-insulator transition in two dimensions to the quantum Hall transition: a percolation-effective-medium theory

Effective-medium theory is applied to the percolation description of the metal-insulator transition in two dimensions with emphasis on the continuous connection between the zero-magnetic-field transition and the quantum Hall transition. In this model the system consists of puddles connected via saddle points, and there is loss of quantum coherence inside the puddles. The effective conductance of the network is calculated using appropriate integration over the distribution of conductances, leading to a determination of the magnetic field dependence of the critical density. Excellent quantitative agreement is obtained with the experimental data, which allows an estimate of the puddle physical parameters

Harnessing van der Waals CrPS4 and Surface Oxides for unique pre-set field induced Exchange Bias in Fe3GeTe2

Two-dimensional van der Waals (vdW) heterostructures are an attractive platform for studying exchange bias due to their defect free and atomically flat interfaces. Chromium thiophosphate (CrPS4), an antiferromagnetic material, possesses uncompensated magnetic spins in a single layer, rendering it a promising candidate for exploring exchange bias phenomena. Recent findings have highlighted that naturally oxidized vdW ferromagnetic Fe3GeTe2 exhibits exchange bias, attributed to the antiferromagnetic coupling of its ultrathin surface oxide layer (O-FGT) with the underlying unoxidized Fe3GeTe2. Anomalous Hall measurements are employed to scrutinize the exchange bias within the CrPS4/(O-FGT)/Fe3GeTe2 heterostructure. This analysis takes into account the contributions from both the perfectly uncompensated interfacial CrPS4 layer and the interfacial oxide layer. Remarkably, a distinct and non-monotonic exchange bias trend is observed as a function of temperature below 140 K. Intriguingly, a pre-set field-induced exchange bias suggests that the predominant phase in the polycrystalline surface oxide is ferrimagnetic Fe3O4. Moreover, the exchange bias induced by the ferrimagnetic Fe3O4 is significantly modulated by the presence of the van der Waals antiferromagnetic CrPS4 layer, forming a heterostructure, along with additional iron oxide phases within the oxide layer. These findings underscore the intricate and unique nature of exchange bias in van der Waals heterostructures, highlighting their potential for tailored manipulation and control

The Use of Heat Treatment to Improve the Quality of Lentil Protein as Ruminant Feed

The objective of this study was to determine the best method of heat treatment (microwave vs. conventional oven) to improve the quality of lentil protein. Lentil samples were either microwaved for 1, 2, or 3 minutes or roasted for 1, 2, or 3 hours at 165̊ F. All the samples and the control were incubated in two cows for 12 hours to determine protein disappearance. The differences between original and residual crude protein content was used to determine the amount of rumen degradable (RDP) and undegradable protein (RUP). The different roasting times had no effect (P = 0.56) on RDP and RUP content. Similarly, the microwaving treatments had no effect (P = 0.41) on RDP and RUP content. In conclusion, none of the treatments tested increased the amount of bypass protein (RUP); therefore, there is a need for research on the use of other methods

Separating spin torque and heating effects in current-induced domain wall motion probed by high-resolution transmission electron microscopy

Observations of domain wall motion and transformations due to injected current pulses in permalloy zigzag structures using off-axis electron holography and Lorentz microscopy are reported. Heating on membranes leads to thermally activated random behavior at low current densities and by backcoating the SiN membranes with Al, heating effects are significantly reduced. A set of indicators is devised to separate unambiguously spin torque effects from heating and it is shown that by using the Al layer the structures are sufficiently cooled to exhibit current-induced domain wall motion due to spin torque

Large-Scale Synthesis of Single-Crystalline Iron Oxide Magnetic Nanorings

We present an innovative approach to the production of single-crystal iron oxide nanorings employing a solution-based route. Single-crystal hematite (alpha-Fe2O3) nanorings were synthesized using a double anion-assisted hydrothermal method (involving phosphate and sulfate ions), which can be divided into two stages: (1) formation of capsule-shaped alpha-Fe2O3 nanoparticles and (2) preferential dissolution along the long dimension of the elongated nanoparticles (the c axis of alpha-Fe2O3) to form nanorings. The shape of the nanorings is mainly regulated by the adsorption of phosphate ions on faces parallel to c axis of alpha-Fe2O3 during the nanocrystal growth, and the hollow structure is given by the preferential dissolution of the alpha-Fe2O3 along the c axis due to the strong coordination of the sulfate ions. By varying the ratios of phosphate and sulfate ions to ferric ions, we were able to control the size, morphology, and surface architecture to produce a variety of three-dimensional hollow nanostructures. These can then be converted to magnetite (Fe3O4) and maghemite (gamma-Fe2O3) by a reduction or reduction-oxidation process while preserving the same morphology. The structures and magnetic properties of these single-crystal alpha-Fe2O3, Fe3O4, and gamma-Fe2O3 nanorings were characterized by various analytical techniques. Employing off-axis electron holography, we observed the classical single-vortex magnetic state in the thin magnetite nanorings, while the thicker rings displayed an intriguing three-dimensional magnetic configuration. This work provides an easily scaled-up method for preparing tailor-made iron oxide nanorings that could meet the demands of a variety of applications ranging from medicine to magnetoelectronics.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000263320400035&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Chemistry, MultidisciplinarySCI(E)EIPubMed293ARTICLE5016968-1697713

Ultrafast Optical Demagnetization manipulates Nanoscale Spin Structure in Domain Walls

During ultrafast demagnetization of a magnetically ordered solid, angular momentum has to be transferred between the spins, electrons, and phonons in the system on femto and picosecond timescales. Although the intrinsic spin transfer mechanisms are intensely debated, additional extrinsic mechanisms arising due to nanoscale heterogeneity have only recently entered the discussion. Here we use femtosecond X ray pulses from a free electron laser to study thin film samples with magnetic domain patterns. We observe an infrared pump induced change of the spin structure within the domain walls on the sub picosecond timescale. This domain topography dependent contribution connects the intrinsic demagnetization process in each domain with spin transport processes across the domain walls, demonstrating the importance of spin dependent electron transport between differently magnetized regions as an ultrafast demagnetization channel. This pathway exists independent from structural inhomogeneities such as chemical interfaces, and gives rise to an ultrafast spatially varying response to optical pump pulse