Highly sensitive microwave devices that are operational at room temperature are important for high-speed multiplex telecommunications. Quantum devices such as superconducting bolometers possess high performance but work only at low temperature. On the other hand, semiconductor devices, although enabling high-speed operation at room temperature, have poor signal-to-noise ratios. In this regard, the demonstration of a diode based on spin-torque-induced ferromagnetic resonance between nanomagnets represented a promising development, even though the rectification output was too small for applications (1.4 mV mW(-1)). Here we show that by applying d.c. bias currents to nanomagnets while precisely controlling their magnetization-potential profiles, a much greater radiofrequency detection sensitivity of 12,000 mV mW(-1) is achievable at room temperature, exceeding that of semiconductor diode detectors (3,800 mV mW(-1)). Theoretical analysis reveals essential roles for nonlinear ferromagnetic resonance, which enhances the signal-to-noise ratio even at room temperature as the size of the magnets decreases.
Electric fields at interfaces exhibit useful phenomena, such as switching functions in transistors, through electron accumulations and/or electric dipole inductions. We find one potentially unique situation in a metal–dielectric interface in which the electric field is atomically inhomogeneous because of the strong electrostatic screening effect in metals. Such electric fields enable us to access electric quadrupoles of the electron shell. Here we show, by synchrotron X-ray absorption spectroscopy, electric field induction of magnetic dipole moments in a platinum monatomic layer placed on ferromagnetic iron. Our theoretical analysis indicates that electric quadrupole induction produces magnetic dipole moments and provides a large magnetic anisotropy change. In contrast with the inability of current designs to offer ultrahigh-density memory devices using electric-field-induced spin control, our findings enable a material design showing more than ten times larger anisotropy energy change for such a use and highlight a path in electric-field control of condensed matter.
Abstract:We have investigated the transport characteristics of dehydroepiandrosterone sulfate (DHEAS), a neuroactive steroid, at the blood-brain barrier (BBB) 3 H]DHEAS across the BBB (118 l/min-g of brain) was 10.4-fold greater than its influx clearance estimated by the in situ brain perfusion technique (11.4 l/min-g of brain), suggesting that DHEAS is predominantly transported from the brain to blood across the BBB. In cellular uptake studies using a conditionally immortalized mouse brain capillary endothelial cell line (TM-BBB4), [3 H]DHEAS uptake by TM-BBB4 cells exhibited a concentration dependence with a K m of 34.4 M and was significantly inhibited by the oatp2-specific substrate digoxin. Conversely, [ 3 H]digoxin uptake by TM-BBB4 cells was significantly inhibited by DHEAS. Moreover, the net uptake of [ 3 H]DHEAS at 30 min was significantly increased under ATP-depleted conditions, suggesting that an energy-dependent efflux process may also be involved in TM-BBB4. RT-PCR and sequence analysis suggest that an oatp2 is expressed in TM-BBB4 cells. In conclusion, DHEAS efflux transport takes place across the BBB, and studies involving in vitro DHEAS uptake and RT-PCR suggest that there is oatp2-mediated DHEAS transport at the BBB. Key Words: Blood-brain barrier-Dehydroepiandrosterone sulfate -Efflux transport-Organic anion transporting polypeptide 2-Conditionally immortalized mouse brain capillary endothelial cell line.
The fully relativistic single-site Green function is derived for generally shaped and magnetically polarized cell potentials. It is shown that the rightand left-hand-side (i.e. , ket and bra) solutions of the Dirac equations are the necessary ingredients and their generalized Wronskian relation provides important identities, which play a decisive role in the construction of the Green function.
Magnetic skyrmions are expected to be promising candidates for information carriers in spintronic devices. In previous work, precise position control of skyrmions has been the main focus of attention for memory and logic applications. Here, with the aim of employing the thermally activated random walk of skyrmion bubbles for logical operations, i.e., token-based Brownian computing, we investigated the dynamics of skyrmion bubbles in W/FeB/Ir/MgO structures. In addition to the observation of Brownian motion of skyrmion bubbles, we demonstrated the electrical control of the diffusion constant by voltage applications. The developed technique would be useful for various kinds of skyrmion-based spintronic devices as well as Brownian computing.
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