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Ferromagnetic sandwiches were studied to determine the domain duplication process, and address the effects of residual domains on nucleation field of hard electrodes.

Recently, the study of interactions between electron spins and heat currents has given rise to the field of "Spin Caloritronics". Experimental studies of these interactions have shown a possibility to combine the use of heat and light to power magnetic tunnel junction (MTJ) devices. Here we present a careful study of an MTJ device on Si substrate that can be powered entirely by light. We analyze the influence of the material properties, device geometry, and laser characteristics on the electric response of the sample. We demonstrate that by engineering the MTJ and its electrical contact, a large photovoltage reaching 100mV can be generated. This voltage originates from the Si substrate and depends on the MTJ magnetic configuration. Finally, we discuss the origin of the photo-voltage in terms of Seebeck and photovoltaic effects. [ABSTRACT FROM AUTHOR]

Structural and magnetic characterizations are performed on exchange-biased multilayers, namely, Ta/X/IrNm/Y/Ta where X and Y are Py and Co. A direct link is observed between the exchange bias variation with temperature and the magnetic disorder.

Research into magnetostatic interactions between the soft and the hard magnetic electrodes in magnetic tunnel junctions using artificial ferrimagnets is presents. The local stray fields linked with domain wall situated in the AFi layers were found to be responsible to the local pinning of domain wall in the detection layer during its reversal.

Research into micromagnetic characteristics arising during the reversal of an artificial ferrimagnet used as a hard layer of a magnetic tunnel junction is presented. An analytical model has been developed which takes account of different tunneling paths linked with local magnetization structures.

The magnetic properties of submicron circular epitaxial Co dot arrays fabricated by electron beam lithography are studied as a function of thickness using high resolution magnetic force microscopy. As a function of thickness, in-plane single domain, vortex, or perpendicular multidomain phases are identified.

The association between the magnetic properties of self-organized cobalt particles and their microscopic structure was analyzed. Findings showed that during the first stages of growth, the film consisted of islands which grew in size and height as a function of cobalt thickness to the final stage of continuous film formation above which particles still develop. The magnetic properties were strongly affected by the particle-shaped cobalt films.

A study was conducted to analyze a new technique for pinning the magnetization of the magnetically hard subsystem in micron-size magnetic tunnel junctions. The tunnel barriers were formed by sputter etching deposited aluminum layers in a rf Ar/O2 plasma. Wafers were then patterned into arrays of square junctions. Experimental results indicated that the tunnel magnetoresistance was independent of the junction size.

Several studies are conducted to explain the angular dependence exhibited by the tunnel magnetoresistance of the different magnetic tunnel junctions . The observed angular dependence is shown to be highly affected by the applied voltage.

Magnetic discussion on Fe/MgO/Fe magnetic tunnel junctions, show an evidence of room temperature antiferromagnetic coupling between two ferromagnetic layers across a very thin insulating barrier. The antiferromagnetic coupling is observed are in good agreement with the equilibrium interlayer exchange theory by spin polarized quantum tunneling of electrons between the ferromagnetic layers.

Tunnel magnetoresistance explains how both the approaches are compatible and compare the extracted polarizations to those computed with a rigorous free electron model. The domain of validity of the Julliere model and its picture of separated electrodes is limited to resistive enough junctions.

Magnetic tunnel junctions are fabricated, that use Co/Ru/Co and Co/Ru/CoFe artificial ferrimagnet (AFi) systems as hard magnetic electrodes. Together with the enhanced thermal stability, up to 350 degree Celsius of the junctions involving the Co/Ru/CoFe system potential use as magnetic sensors is discussed.

The impact of the micromagnetic configuration within the ferromagnetic layers on transport properties of hard/soft magnetic tunnel junctions is presented. An artificial ferrimagnetic (AFi) trilayer structure is used as a magnetically hard subsystem.

The propagation of a domain wall in a submicron ferromagnetic spin-valve stripe is investigated using giant magnetoresistance. A notch in the stripe efficiently traps an injected wall stopping the domain propagation. The authors show that the magnetic field at which the wall is depinned displays a stochastic nature. Moreover, the depinning statistics are significantly different for head-to-head and tail-to-tail domain walls. This is attributed to the dipolar field generated in the vicinity of the notch by the pinned layer of the spin valve. [ABSTRACT FROM AUTHOR]

We report on room temperature 1/f noise in fully epitaxial Fe (45 nm)/MgO (2.6 nm)/Fe (10 nm) magnetic tunnel junctions (MTJs) with and without carbon doping of the Fe/MgO bottom interface. We have found that the normalized noise (Hooge factor) asymmetry between parallel and antiparallel states may strongly depend on the applied bias and its polarity. Both types of MTJs exhibit record of low Hooge factors being at least one order of magnitude smaller than previously reported. [ABSTRACT FROM AUTHOR]

The association of an antiferromagnetic material with a ferromagnetic material in an exchange coupled bilayer is used as a detection layer in a tunnel magnetoresistive sensor. The magnetic response is shown to be reversible and linear depending on the field range to be measured. Both tunnel magnetoresistance and exchange field decrease linearly with the temperature and lead to temperature independent sensor sensibility. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]