Jean-Luc Duvail

Calculation of the temperature dependence of the giant MR and application to Co/Cu multilayers

Most theoretical models of the giant magnetoresistance (GMR) in metallic magnetic multilayers developed up to now are for the zero‐temperature limit, thus neglecting the spin‐flip scattering arising from spin fluctuations (magnons), as well as other scatterings from thermal excitations. To account for the temperature dependence of the GMR, we have introduced electron–magnon and electron–phonon scattering terms in a Camley–Barnas‐like semi‐classical model. We apply our calculation to the interpretation of the temperature dependence of the resistivity and GMR in Co/Cu.

Perpendicular magnetic anisotropy in CoxPd1−x alloy films grown by molecular beam epitaxy

We have grown face‐centered cubic (FCC) (111)‐ and (001)‐oriented CoxPd1−x alloy films (x≊0.20–0.25) by molecular beam epitaxy on (111)Si and (001)MgO substrates, respectively, with thicknesses ≊200–1000 A. Magnetization (SQUID) measurements show that both (111) and (100) films present a perpendicular easy axis, indicating that a strong magnetic anisotropy overcomes the demagnetizing field favoring the in‐plane orientation. We have studied this magnetic anisotropy by combining SQUID and torque measurements. Our experimental results cannot be accounted for by only invoking the magnetocrystalline anisotropy of a disordered solid solution of Co in FCC Pd, and rather indicate an anisotropic distribution of Co in the Pd host.

Giant magnetoresistance in magnetic nanostructures

Abstract Since its discovery in magnetic multilayers, the giant magnetoresistance has become one major research topic in both applied and pure magnetism. At first, new theories had to be devised to explain the oscillating indirect exchange coupling and to understand how spin-dependent transport properties give rise to the giant magnetoresistance. Also, because the magnetic multilayer where, at the time, a new class of materials, a lot of attention has been devoted to the study of their structural properties. In this paper, we review some experimental results and theoretical models on GMR in magnetic multilayers. Then, we present an overview of the giant magnetoresistance in new nanostructures - granular alloys and hybrid systems - with magnetic entities in the form of clusters instead of layers.

Giant magnetoresistance in hybrid nanostructures

Abstract We describe the Giant Magnetoresistance (GMR) properties of multilayered structures including continuous layers of permalloy (Ni80Fe20) and discontinuous layers of cobalt separated by layers of copper or silver. These hybrid structures exhibit large GMR ratios with high slopes at low field (as high as 7%/Oe). They are also very convenient for an accurate determination of the angular dependence of the GMR and interesting to discuss the origin of the GMR. We finally analyse GMR measurements performed with the current perpendicular to the layers and separate the bulk and interface contributions.

Treatment of the semiclassical Boltzmann equation for magnetic multilayers

We present an analytical treatment of the Camley–Barnaś theory of the giant magnetoresistance (GMR) in magnetic layered structures and obtain an exact and general expression for the resistivity. We used this expression to evaluate the resistivity and GMR numerically, comparing the results with experimental observations.

A new multilayer system: Pd1-xCox Ag

Abstract In Co 0.3 Pd 0.7 Ag superlattices grown by molecular beam epitaxy, we have observed a crossover from out- to in-plane magnetization for CoPd thicknesses below 50 mA and found a magnetoresistance of 13% at 4.2 K correlated with an antiferromagnetic alignment between successive CoPd magnetic layers.

Oscillatory interlayer exchange and giant magnetoresistance in magnetic multilayers

We discuss two properties of magnetic multilayers, namely the giant magnetoresistance effect and the oscillation of the magnetic coupling between magnetic layers as a function of the thickness of the non‐magnetic spacer. They are illustrated by results obtained in Fe/Cr, Co/Cu, and Fe/Cu multilayers, and a review of the theoretical models dealing with these phenomena is given. Finally, some recently developed magnetic nanostructures with promising performance as field sensing devices are briefly described.