Spin-polarized tunneling in ferromagnetic double barrier junctions

Spin-polarized tunneling in FMS/M/FMS double tunnel junctions where FMSs are ferromagnetic semiconductor layers and M is a metal spacer is studied theoretically within the single-site coherent potential approximation (CPA). The exchange interaction between a conduction electron and localized moment of the magnetic ion is treated in the framework of the s-f model. The spin polarization in the FMS layers is observed to oscillates as a function of the number of atomic planes in the spacer layer. Amplitude of these oscillations decreases with increasing the exchange interaction in FMS layers. Received 9 June 2001 and Received in final form 20 August 2001     

Investigation of ripple structures of thin polycrystalline Co films by magnetic force microscopy

Received: 14 August 1997/Accepted: 14 August 1997     

Ferromagnetism in the Hubbard model on fcc-type lattices

The Hubbard model on fcc-type lattices is studied in the dynamical mean-field theory of infinite spatial dimensions. At intermediate interaction strength finite temperature Quantum Monte Carlo calculations yield a second order phase transition to a highly polarized, metallic ferromagnetic state. The Curie temperatures are calculated as a function of electronic density and interaction strength. A necessary condition for ferromagnetism is a density of state with large spectral weight near one of the band edges. Received: 6 August 1997 / Accepted: 20 August 1997     

Ultrashort pulse laser ablation of silicon: an MD simulation study

Received: 30 July 1997/Accepted: 5 August 1997     

Proximity effect in Fe/Pb/Fe trilayers

We have studied superconducting and magnetic properties of sputtered Fe/Pb/Fe-trilayers. For a fixed Pb thickness and with changing Fe thickness, , a monotonic decrease of the superconducting transition temperature was observed. Magnetization measurements clearly showed that Fe remains ferromagnetic down to the monolayer range. A quantitative comparison of with the theory of pair breaking by the exchange field reveals that the observed -suppression by the ferromagnetic Fe-layer is much weaker than expected. Possible reasons for the reduced -suppression in this system are discussed. Received: 30 June 1997 / Revised: 20 August 1997 / Accepted: 16 December 1997     

On the dynamic interaction between moving dislocations

Received: 25 August 1997/Accepted: 23 October 1997     

Ferromagnetic ground state in the Kondo lattice model

We present a series of rigorous examples of the Kondo lattice model that exhibit full ferromagnetism in the ground state. The models are defined in one-, two- and three-dimensional lattices, and are characterized by a range of hopping terms, specific electron filling, and large ferromagnetic coupling. Our examples show that a sufficient strong but finite exchange coupling between conduction electrons and localized spins could overcome the competition from mobility of a finite density of electrons and drive the system from a paramagnetic phase to a ferromagnetic phase. We also establish a relation of ferromagnetism between the Hubbard model and Kondo lattice model. Meanwhile some rigorous results on ferromagnetism in the corresponding Hubbard model are presented. Received: 10 September 1997 / Revised: 15 October 1997 / Accepted: 17 October 1997     

(e,2e) electron spectroscopy of surfaces

Received: 21 March 1997/Accepted 12 August 1997     

Ion strings for quantum gates

Received: 6 August 1997/Revised version: 21 October 1997     

(4×2) and (2×4) reconstructions of GaAs and InP(001) surfaces

Received: 21 March 1997/Accepted: 12 August 1997     

Theory of EPR on a rotating sample: An illustration of Berry's phase

We describe the theory of EPR in a crystal field multiplet under sample spinning. Berry phases arise because the crystal field is of lower symmetry than the full rotation group. The formal development is limited to pure J multiplets, crystal field doublets, and field and rotation axes parallel to a principal axis. Received: 4 August 1997 / Received in final form: 19 December 1997 / Accepted: 28 January 1998     

On thickness dependence of electrical and optical properties of Te thin films

Received: 1 July 1997/Accepted: 6 August 1997     

Effects of temperature and pressure on CVD diamond growth from the C-H-O system

Received: 28 August 1997/Accepted: 18 November 1997     

Measuring the temporal intensity of ultrashort laser pulses by triple correlation

Received: 13 May 1997/Revised version: 1 August 1997     

Recurring dark states in Ramsey-type subrecoil cooling

Received: 30 May 1997/Revised version: 26 August 1997     

Multiple beam atom interferometer: theory and experiment

Received: 30 May 1997/ 27 August 1997     

Nanocrystalline-grained Bi-Sr-Ca-Cu-O and its superconducting property

Received: 5 August 1997/Accepted: 2 October 1997     

Wealth distributions in asset exchange models

A model for the evolution of the wealth distribution in an economically interacting population is introduced, in which a specified amount of assets are exchanged between two individuals when they interact. The resulting wealth distributions are determined for a variety of exchange rules. For “random” exchange, either individual is equally likely to gain in a trade, while “greedy” exchange, the richer individual gains. When the amount of asset traded is fixed, random exchange leads to a Gaussian wealth distribution, while greedy exchange gives a Fermi-like scaled wealth distribution in the long-time limit. Multiplicative processes are also investigated, where the amount of asset exchanged is a finite fraction of the wealth of one of the traders. For random multiplicative exchange, a steady state occurs, while in greedy multiplicative exchange a continuously evolving power law wealth distribution arises. Received: 13 August 1997 / Revised: 31 December 1997 / Accepted: 26 January 1998     

Positronium–oxygen interactions in polytrimethylsilylpropine membranes

Received: 25 April 1997/Revised version: 1 August 1997     

Plasmon resonances in a spherical sodium cluster and in a flat surface with a soft optical edge

Received: 27 August 1997/Revised version: 7 November 1997