J. B. Sousa

Magnetoresistance enhancement in specular, bottom-pinned, Mn83Ir17 spin valves with nano-oxide layers

Bottom-pinned Mn83Ir17 spin valves with enhanced specular scattering were fabricated, showing magnetoresistance (MR) values up to 13.6%, lower sheet resistance R□ and higher ΔR□. Two nano-oxide layers (NOL) are grown on both sides of the CoFe/Cu/CoFe spin valve structure by natural oxidation or remote plasma oxidation of the starting CoFe layer. Maximum MR enhancement is obtained after just 1 min plasma oxidation. Rutherford backscattering analysis shows that a 15±2 A oxide layer grows at the expense of the initial (prior to oxidation) CoFe layer, with ∼12% reduction of the initial 40 A CoFe thickness. X-ray reflectometry indicates that Kiessig fringes become better defined after NOL growth, indicating smoother inner interfaces, in agreement with the observed decrease of the spin valve ferromagnetic Neel coupling.

Tunnel magnetoresistance and magnetic ordering in ion-beam sputtered Co80Fe20/Al2O3 discontinuous multilayers

Discontinuous multilayered Co80Fe20(t)/Al2O3(30 A) thin films have been prepared by ion-beam sputtering. We report on structural, magnetic, and transport (for current in plane geometry) results obtained in this system. With growing nominal thickness t of the metal layers, which effectively characterizes the granular structure, a transition from tunnel to metallic conductance is observed, indicating the onset of infinite conducting paths at t>18 A. At t 13 A was detected from the magnetization data which display here a transition from superparamagnetic to ferromagnetic behavior. The measurements of tunnel magnetoresistance (MR) show that a sharp maximum of MR sensitivity to field takes place at this thickness, reaching ∼24%/kOe at room temperature. At least, MR itself as a function of t has a break at the same value. All these features suggest that some specific kind of percolation with respect to magnetic order occurs in o...

Ferromagnetic resonance in granular thin films

A theoretical analysis has been done of the effects of granule size, shape, orientation, and concentration and the temperature effects on the ferromagnetic resonance (FMR) field Hr in granular thin films. The granular CoxAg1−x thin films with 0.2 fp. For the Co–Ag system, persistence of a considerable SPM fraction is revealed by the superconducting quantum interference device data up to the highest f, and the effect at f=fp consists in a discontinuous jump of the Hr(f) slope. Otherwise, the FMR data for granular Fe–SiO2 films reveal a discontinuous jump in H...

Search Strategies for Multiple UAV Search and Destroy Missions

Multiple UAVs are deployed to carry out a search and destroy mission in a bounded region. The UAVs have limited sensor range and can carry limited resources which reduce with use. The UAVs perform a search task to detect targets. When a target is detected which requires different type and quantities of resources to completely destroy, then a team of UAVs called as a coalition is formed to attack the target. The coalition members have to modify their route to attack the target, in the process, the search task is affected, as search and destroy tasks are coupled. The performance of the mission is a function of the search and the task allocation strategies. Therefore, for a given task allocation strategy, we need to devise search strategies that are efficient. In this paper, we propose three different search strategies namely; random search strategy, lanes based search strategy and grid based search strategy and analyze their performance through Monte-Carlo simulations. The results show that the grid based search strategy performs the best but with high information overhead.

Neptus - a framework to support multiple vehicle operation

This paper describes the development of a C3I (communications, command, control and intelligence/information) infrastructure, taking place at the Underwater Systems and Technology Laboratory (LSTS) of FEUP. This infrastructure, the Neptus framework, goal is to support the coordinated operation of heterogeneous teams, which include autonomous and remotely operated underwater, surface, land, and air vehicles and people. People perform a fundamental role, not only in the case of remotely operated vehicles, but also with autonomous vehicles where mix-initiative operation is a requirement. The operational scenarios for these teams are mainly environmental monitoring missions but could also include environmental disaster scenarios, rescue missions, etc. The Neptus distributed architecture is service oriented, which enables high degrees of interoperability between applications, of scalability (number of nodes), and of reconfiguration (number and type of nodes).

Electromigration in thin tunnel junctions with ferromagnetic/nonmagnetic electrodes: Nanoconstrictions, local heating, and direct and wind forces

Current Induced Resistance Switching (CIS) was recently observed in thin tunnel junctions with ferromagnetic (FM) electrodes, i.e., FM/I/FM. This effect was attributed to electromigration of metallic atoms in nanoconstrictions in the insulating barrier (I). Here we study how the CIS effect is influenced by a thin nonmagnetic (NM) Ta layer, deposited just below the

A new ROV design: issues on low drag and mechanical symmetry

\mathrm{Al}{\mathrm{O}}_{x}

Electroforming, magnetic and resistive switching in MgO-based tunnel junctions

insulating barrier in tunnel junctions of the type FM/NM/I/FM

Ferromagnetic coupling field reduction in CoFeB tunnel junctions deposited by ion beam

(\mathrm{FM}\mathrm{Co}\mathrm{Fe})

Transport properties of discontinuous cCo/sub 80/Fe/sub 20//Al/sub 2/O/sub 3/ multilayers prepared by ion beam sputtering

. Enhanced resistance switching occurs with increasing maximum applied current