Ultrafast spin exchange-coupling torque via photo-excited charge-transfer processes

Optical control of spin is of central importance in the research of ultrafast spintronic devices utilizing spin dynamics at short time scales. Recently developed optical approaches such as ultrafast demagnetization, spin-transfer and spin-orbit torques open new pathways to manipulate spin through its interaction with photon, orbit, charge or phonon. However, these processes are limited by either the long thermal recovery time or the low-temperature requirement. Here we experimentally demonstrate ultrafast coherent spin precession via optical charge-transfer processes in the exchange-coupled Fe/CoO system at room temperature. The efficiency of spin precession excitation is significantly higher and the recovery time of the exchange-coupling torque is much shorter than for the demagnetization procedure, which is desirable for fast switching. The exchange coupling is a key issue in spin valves and tunnelling junctions, and hence our findings will help promote the development of exchange-coupled device concepts for ultrafast coherent spin manipulation

Martian ionospheric responses to dynamic pressure enhancements in the solar wind

As a weakly magnetized planet, Mars ionosphere/atmosphere interacts directly with the shocked solar wind plasma flow. Even though many numerical studies have been successful in reproducing numerous features of the interaction process, these earlier studies focused mainly on interaction under steady solar wind conditions. Recent observations suggest that plasma escape fluxes are significantly enhanced in response to solar wind dynamic pressure pulses. In this study, we focus on the response of the ionosphere to pressure enhancements in the solar wind. Through modeling of two idealized events using a magnetohydrodynamics model, we find that the upper ionosphere of Mars responds almost instantaneously to solar wind pressure enhancements, while the collision dominated lower ionosphere (below ~150 km) does not have noticeable changes in density. We also find that ionospheric perturbations in density, magnetic field, and velocity can last more than an hour after the solar wind returns to the quiet conditions. The topside ionosphere forms complicated transient shapes in response, which may explain unexpected ionospheric behaviors in recent observations. We also find that ionospheric escape fluxes do not correlate directly with simultaneous solar wind dynamic pressure. Rather, their intensities also depend on the earlier solar wind conditions. It takes a few hours for the ionospheric/atmospheric system to reach a new quasi‐equilibrium state. Key Points This paper studies ionospheric responses to solar wind pressure enhancements The ionosphere forms complicated transient shapes when solar wind varies The escape fluxes depend on both simultaneous and earlier solar wind conditionsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106668/1/jgra50802.pd

Systematic studies of binding energy dependence of neutron - proton momentum correlation function

Hanbury Brown-Twiss (HBT) results of the neutron-proton correlation function have been systematically investigated for a series nuclear reactions with light projectiles with help of Isospin-Dependent Quantum Molecular Dynamics model. The relationship between the binding energy per nucleon of the projectiles and the strength of the neutron-proton HBT at small relative momentum has been obtained. Results show that neutron-proton HBT results are sensitive to the binding energy per nucleon.Comment: 10 pages, 5 figures; accepted by Journal of Physics G: Nuclear and Particle Physic

Current-driven interface magnetic transition in complex oxide heterostructure

The interfacial spin state of n-type BaTiO3/La0.5Ca0.5MnO3/La0.7Sr0.3MnO3 heterojunction and its dependence on gate voltage is investigated with magnetic second-harmonic generation at 78 K. The injection of minority spins alters the interface magnetization of La0.7Sr0.3MnO3 from ferromagnetic to antiferromagnetic exchange coupled, while the bulk magnetization remains unchanged. The emergent interfacial antiferromagnetic interactions are attributed to modulations of the strong double-exchange interaction between conducting electron spins and local magnetic moments. The results will help promote the development of new interface-based functionalities and device concepts. (C) 2017 American Vacuum Society

Total Reaction Cross Section in an Isospin-Dependent Quantum Molecular Dynamics (IDQMD) Model

The isospin-dependent quantum molecular dynamics (IDQMD) model is used to study the total reaction cross section $\sigma_R$. The energy-dependent Pauli volumes of neutrons and protons have been discussed and introduced into the IDQMD calculation to replace the widely used energy-independent Pauli volumes. The modified IDQMD calculation can reproduce the experimental $\sigma_R$ well for both stable and exotic nuclei induced reactions. Comparisons of the calculated $\sigma_R$ induced by $^{11}Li$ with different initial density distributions have been performed. It is shown that the calculation by using the experimentally deduced density distribution with a long tail can fit the experimental excitation function better than that by using the Skyrme-Hartree-Fock calculated density without long tails. It is also found that $\sigma_R$ at high energy is sensitive to the long tail of density distribution.Comment: 4 page, 4 fig

Combination of acupuncture and Chinese medicinal herbs in treating model rats with Polycystic Ovary Syndrome

We explored the effects of combination of acupuncture and Chinese medicinal herbs in treating model rats with polycystic ovarian syndrome (PCOS) and to explore whether acupuncture has positive effects on the absorption of salvianolic acid B in the extracts of a Chinese medicine formula when treating the model rats. 60 female Sprague–Dawley (SD) rats were randomly divided into Groups A, B, C, D, E and F, with ten rats in each group. Except Group F, all of the other rats were induced to PCOS with oral administration of letrozole. The rats in Group F served as normal controls. Group A was treated with acupuncture. Group B was treated with oral administration of the extracts of the Chinese medicine formula. Group C was treated with a combination of oral administration of the extracts of Chinese medicine and acupuncture. Group D received western medicine as positive controls. After treatment, the serum levels of follicle stimulating hormone (FSH), luteinizing hormone(LH) and testosterone (T) in each group were detected with the Enzyme-Linked ImmunoSorbent Assay (ELISA) and the serum concentration of salvianolic acid B were determined using High Performance Liquid Chromatography (HPLC). The serum levels of T and the ratio of LH/FSH in Group A, B. C, D, and F were significantly lower than those of Group E, indicating the model rats with PCOS were successfully established. Compared with Groups A, B, D and E, the serum levels of T and the ratio of LH/FSH in Group C were significantly lower respectively, indicating combination of acupuncture and Chinese medicinal herbs can significantly enhance curative effects in treating model rats with PCOS. The concentration of serum salvianolic acid Group C was significantly higher than Group B, indicating that acupuncture might improve the absorption of salvianolic acid B from the extracts of Salvia miltiorrhiza Bunge in the Chinese medicine formula. Combination of acupuncture and Chinese medicinal herbs significantly enhance curative effects in treating model rats with PCOS and acupuncture has positive effects in improving the absorption of salvianolic acid B in the extracts of the Chinese medicine formula when treating the model rats with PCOS.Key words: Acupuncture; Chinese medicine; Polycystic ovarian syndrome (PCOS).doi: 10.4314/ajtcam.v8i4.

Interface magnetization transition via minority spin injection

The interface magnetization of n-type BaTiO3/La0.7Sr0.3MnO3 heterojunction is selectively probed by magnetic second-harmonic generation at 80 K. The injection of minority spins at the interface causes a sudden, reversible transition of the spin alignment of interfacial Mn ions from ferromagnetic to antiferromagnetic exchange coupled, while the bulk magnetization remains unchanged. We attribute the emergent interfacial antiferromagnetic interactions to weakening of the double-exchange mechanism caused by the strong Hund\u27s rule coupling between injected minority spins and local magnetic moments. The effect is robust and may serve as a viable route for electronic and spintronic applications. Published by AIP Publishing