Effect of spin relaxations on the spin mixing conductances for a bilayer structure

The spin current can result in a spin-transfer torque in the normal-metal(NM)|ferromagnetic-insulator(FMI) or normal-metal(NM)|ferromagnetic-metal(FMM) bilayer. In the earlier study on this issue, the spin relaxations were ignored or introduced phenomenologically. In this paper, considering the FMM or FMI with spin relaxations described by a non-Hermitian Hamiltonian, we derive an effective spin-transfer torque and an effective spin mixing conductance in the non-Hermitian bilayer. The dependence of the effective spin mixing conductance on the system parameters (such as insulating gap, \textit{s-d} coupling, and layer thickness) as well as the relations between the real part and the imaginary part of the effective spin mixing conductance are given and discussed. We find that the effective spin mixing conductance can be enhanced in the non-Hermitian system. This provides us with the possibility to enhance the spin mixing conductance

Evolution of magnetic properties in the vicinity of the Verwey transition in Fe3O4 thin films

We have systematically studied the evolution of magnetic properties, especially the coercivity and the remanence ratio in the vicinity of the Verwey transition temperature (TV ), of high-quality epitaxial Fe3O4 thin films grown on MgO (001), MgAl2O4 (MAO) (001), and SrTiO3 (STO) (001) substrates. We observed rapid change of magnetization, coercivity, and remanence ratio at TV , which are consistent with the behaviors of resistivity versus temperature [\r{ho}(T )] curves for the different thin films. In particular, we found quite different magnetic behaviors for the thin films onMgOfrom those onMAOand STO, inwhich the domain size and the strain state play very important roles. The coercivity is mainly determined by the domain size but the demagnetization process is mainly dependent on the strain state. Furthermore, we observed a reversal of remanence ratio at TV with thickness for the thin films grown on MgO: from a rapid enhancement for 40-nm- to a sharp drop for 200-nm-thick film, and the critical thickness is about 80 nm. Finally, we found an obvious hysteretic loop of coercivity (or remanence ratio) with temperature around TV , corresponding to the hysteretic loop of the \r{ho}(T ) curve, in Fe3O4 thin film grown on MgO

Geometric phases in a scattering process

The study of geometric phase in quantum mechanics has so far be confined to discrete (or continuous) spectra and trace preserving evolutions. Consider only the transmission channel, a scattering process with internal degrees of freedom is neither a discrete spectrum problem nor a trace preserving process. We explore the geometric phase in a scattering process taking only the transmission process into account. We find that the geometric phase can be calculated by the some method as in an unitary evolution. The interference visibility depends on the transmission amplitude. The dependence of the geometric phase on the barrier strength and the spin-spin coupling constant is also presented and discussed.Comment: 4 pages, 5 figure

Production interdependence and welfare

The international welfare effects of a country's monetary policy shocks have been controversial in the new open economy macro (i.e., NOEM) literature. While a unilateral monetary expansion increases the production efficiency in each country, it affects the terms of trade in favor of one country against another depending on the currencies of price setting. In this paper, we incorporate multiple stages of production and trade into a standard NEOM model to capture world production interdependence, and show that increased world production interdependence tends to magnify the e±ciency-improvement effect while dampening the terms-of-trade effect. As a consequence, a unilateral monetary expansion can be mutually beneficial regardless of in which currency prices are set. In this sense, international monetary policy transmission may not be a source of potential conflict in a world with production interdependence. JEL Classification: E32, F31, F41Local currency pricing, Monopolistic competition, Stages of processing, Welfare

Inflation targeting: what inflation rate to target?

In an economy with nominal rigidities in both an intermediate good sector and a finished good sector, and thus with a natural distinction between CPI and PPI inflation rates, a benevolent central bank faces a tradeoff between stabilizing the two measures of inflation: a final output gap, and unique to our model, a real marginal cost gap in the intermediate sector, so that optimal monetary policy is second-best. We discuss how to implement the optimal policy with minimal information requirement and evaluate the robustness of these simple rules when the central bank may not know the exact sources of shocks or nominal rigidities. A main finding is that a simple hybrid rule under which the short-term interest rate responds to CPI inflation and PPI inflation results in a welfare level close to the optimum, whereas policy rules that ignore PPI inflation or PPI sector shocks can result in significant welfare losses.Inflation (Finance)

Staggered Contracts and Business Cycle Persistence

Staggered price and staggered wage contracts are commonly viewed as similar mechanisms in generating persistent real effects of monetary shocks. In this paper, we distinguish the two mechanisms in a dynamic stochastic general equilibrium framework. We show that, although the dynamic price setting and wage setting equations are alike, a key parameter governing persistence is linked to the underlying preferences and technologies in different ways. Under the staggered wage mechanism, an intertemporal smoothing incentive in labor supply creates a real rigidity that is absent under the staggered price mechanism. Consequently, the two mechanisms have different implications on persistence. While the staggered price mechanism by itself does not contribute to, the staggered wage mechanism plays an important role in generating persistence.Staggered Contracts; Business Cycle Persistence; Monetary Policy

Mediating exchange bias by Verwey transition in CoO/Fe3O4 thin film

We report the tunability of the exchange bias effect by the first-order metal-insulator transition (known as the Verwey transition) of Fe3O4 in CoO (5 nm)/Fe3O4 (40 nm)/MgO (001) thin film. In the vicinity of the Verwey transition, the exchange bias field is substantially enhanced because of a sharp increase in magnetocrystalline anisotropy constant from high-temperature cubic to lowtemperature monoclinic structure. Moreover, with respect to the Fe3O4 (40 nm)/MgO (001) thin film, the coercivity field of the CoO (5 nm)/Fe3O4 (40 nm)/MgO (001) bilayer is greatly increased for all the temperature range, which would be due to the coupling between Co spins and Fe spins across the interface

'BioNessie(G) - a grid enabled biochemical networks simulation environment

The simulation of biochemical networks provides insight and understanding about the underlying biochemical processes and pathways used by cells and organisms. BioNessie is a biochemical network simulator which has been developed at the University of Glasgow. This paper describes the simulator and focuses in particular on how it has been extended to benefit from a wide variety of high performance compute resources across the UK through Grid technologies to support larger scale simulations