Exchange-torque-induced excitation of perpendicular standing spin waves in nanometer-thick YIG films

Spin waves in ferrimagnetic yttrium iron garnet (YIG) films with ultralow magnetic damping are relevant for magnon-based spintronics and low-power wave-like computing. The excitation frequency of spin waves in YIG is rather low in weak external magnetic fields because of its small saturation magnetization, which limits the potential of YIG films for high-frequency applications. Here, we demonstrate how exchange-coupling to a CoFeB film enables efficient excitation of high-frequency perpendicular standing spin waves (PSSWs) in nanometer-thick (80 nm and 295 nm) YIG films using uniform microwave magnetic fields. In the 295-nm-thick YIG film, we measure intense PSSW modes up to 10th order. Strong hybridization between the PSSW modes and the ferromagnetic resonance mode of CoFeB leads to characteristic anti-crossing behavior in broadband spin-wave spectra. A dynamic exchange torque at the YIG/CoFeB interface explains the excitation of PSSWs. The localized torque originates from exchange coupling between two dissimilar magnetization precessions in the YIG and CoFeB layers. As a consequence, spin waves are emitted from the YIG/CoFeB interface and PSSWs form when their wave vector matches the perpendicular confinement condition. PSSWs are not excited when the exchange coupling between YIG and CoFeB is suppressed by a Ta spacer layer. Micromagnetic simulations confirm the exchange-torque mechanism.Comment: 9 pages, 6 figure

Trapping of 27 bp - 8 kbp DNA and immobilization of thiol-modified DNA using dielectrophoresis

Dielectrophoretic trapping of six different DNA fragments, sizes varying from the 27 to 8416 bp, has been studied using confocal microscopy. The effect of the DNA length and the size of the constriction between nanoscale fingertip electrodes on the trapping efficiency have been investigated. Using finite element method simulations in conjunction with the analysis of the experimental data, the polarizabilities of the different size DNA fragments have been calculated for different frequencies. Also the immobilization of trapped hexanethiol- and DTPA-modified 140 nm long DNA to the end of gold nanoelectrodes was experimentally quantified and the observations were supported by density functional theory calculations.Comment: 17 pages (1 column version), 8 figure

Size Dependence of Domain Pattern Transfer in Multiferroic Heterostructures

Magnetoelectric coupling in multiferroic heterostructures can produce large lateral modulations of magnetic anisotropy enabling the imprinting of ferroelectric domains into ferromagnetic films. Exchange and magnetostatic interactions within ferromagnetic films oppose the formation of such domains. Using micromagnetic simulations and a one-dimensional model, we demonstrate that competing energies lead to the breakdown of domain pattern transfer below a critical domain size. Moreover, rotation of the magnetic field results in abrupt transitions between two scaling regimes with different magnetic anisotropy. The theoretical predictions are confirmed by experiments on CoFeB/BaTiO3 heterostructures.Peer reviewe

Suborbital Payload Testing Aboard Level 3 Rocket Research Platform

Embry-Riddle Aeronautical University (ERAU) has launched several suborbital scientific payloads aboard Blue Origin’s New Shepard in 2017 and 2019. Students continue gaining hands-on experience in rocket design and construction, and payload integration and testing of future and more mature payloads to be launched into space. A Level 3 Rocket is being designed and developed at ERAU to serve as a scaled-down model research platform for launching and testing of payloads that will be later flown in commercial suborbital platforms such as Blue Origin’s New Shepard and PLD space Miura 1 rockets. Computer simulations were conducted to calculate the key parameters such as flight trajectory profiles, stability and flight velocities for different rocket motors configurations. A preliminary design of the rocket was developed using Computer-Aided Design (CAD) software. The rocket will accommodate multiple payloads (Cubesats, NanoLabs, TubeSats) designed and developed in the Payload Applied, Technology and Operations (PATO) laboratory. The rocket will be primarily constructed of carbon fiber composite as it has a high strength to weight ratio. These simulations are used to select a suitable motor for the rocket according to the flight requirements and landing restrictions. This prospective Level 3 Rocket is referred to as Suborbital Technology Experimental Vehicle for Exploration (STEVE). Rocket procedures and results from the design, simulation, construction and assembly will be presented

Reversible Electric-Field-Driven Magnetic Domain-Wall Motion

Control of magnetic domain-wall motion by electric fields has recently attracted scientific attention because of its potential for magnetic logic and memory devices. Here, we report on a new driving mechanism that allows for magnetic domain-wall motion in an applied electric field without the concurrent use of a magnetic field or spin-polarized electric current. The mechanism is based on elastic coupling between magnetic and ferroelectric domain walls in multiferroic heterostructures. Pure electric-field-driven magnetic domain-wall motion is demonstrated for epitaxial Fe films on BaTiO3 with in-plane and out-of-plane polarized domains. In this system, magnetic domain-wall motion is fully reversible and the velocity of the walls varies exponentially as a function of out-of-plane electric-field strength.Peer reviewe

Transcriptional analysis of oligosaccharide utilization by <em>Bifidobacterium lactis</em> Bl-04

BACKGROUND: Probiotic bifidobacteria in combination with prebiotic carbohydrates have documented positive effects on human health regarding gastrointestinal disorders and improved immunity, however the selective routes of uptake remain unknown for most candidate prebiotics. The differential transcriptomes of Bifidobacterium animalis subsp. lactis Bl-04, induced by 11 potential prebiotic oligosaccharides were analyzed to identify the genetic loci involved in the uptake and catabolism of α- and β-linked hexoses, and β-xylosides. RESULTS: The overall transcriptome was modulated dependent on the type of glycoside (galactosides, glucosides or xylosides) utilized. Carbohydrate transporters of the major facilitator superfamily (induced by gentiobiose and β-galacto-oligosaccharides (GOS)) and ATP-binding cassette (ABC) transporters (upregulated by cellobiose, GOS, isomaltose, maltotriose, melibiose, panose, raffinose, stachyose, xylobiose and β-xylo-oligosaccharides) were differentially upregulated, together with glycoside hydrolases from families 1, 2, 13, 36, 42, 43 and 77. Sequence analysis of the identified solute-binding proteins that determine the specificity of ABC transporters revealed similarities in the breadth and selectivity of prebiotic utilization by bifidobacteria. CONCLUSION: This study identified the differential gene expression for utilization of potential prebiotics highlighting the extensive capabilities of Bifidobacterium lactis Bl-04 to utilize oligosaccharides. Results provide insights into the ability of this probiotic microbe to utilize indigestible carbohydrates in the human gastrointestinal tract