Giant Magnetoresistance In Magnetic Multilayers Research Articles

Influence of intralayer quantum-well states on the giant magnetoresistance in magnetic multilayers.

A model which can account for the experimentally observed variations of the giant magnetoresistance in thin magnetic multilayers with mean free path, interface roughness, magnetic layer, and normal layer thickness has been developed. The model requires the existence of quantum-well states within individual layers or groups of layers, depending on the magnetic state of the film. The calculated results are ob tained by the application of quantum size effect transport theory to these individual layers

Giant magnetoresistance with current perpendicular to the multilayer planes

We review recent progress in measuring giant magnetoresistance in magnetic multilayers with the current flowing perpendicular to the multilayer planes (CPP-MR), and present new data for Co/Cu and Co/Ag multilayers.

Theory of the conductivity and giant magnetoresistance in magnetic multilayers.

A simple, analytic expression is derived for the conductivity of thin films with the use of the coherent-potential approximation. With the use of our conductivity formula, the giant magnetoresistance in multilayers consisting of magnetic and nonmagnetic layers, is discussed based on a numerical calculation for seven-layer Fe/Cr films and a phenomenological analysis for a simple model.

Quantum size effect and the giant magnetoresistance in magnetic multilayers

A theoretical model which accounts for the variations of the giant magnetoresistance, Δρ/ρ, with electron mean free path, L, interface roughness, r, and magnetic, tM, and normal layer, tN, thickness has been previously presented for sandwich films. It employs the quantum-size-effect theory of resistivity in thin films and relies on spin dependent transmission or reflection at individual layer boundaries to establish the metallic quantum-well states. This model has now been extended (i) to films where L can be different in the magnetic, LM, and nonmagnetic, LN, layers, (ii) to an electron/atom number, n, of 0.131 as well as 1.047, and (iii) to films from sandwiches to those with as many as 64 (63) magnetic (nonmagnetic) layers. The focus is on films with relatively thin tM and tN where quantum, as distinguished from semiclassical, effects should dominate. Typical results can be summarized as follows: for tM∼tN∼10 monolayers, ML, and L’s∼70 ML, Δρ/ρ increases more rapidly as LM than LN, but this effect is reduced as one goes from sandwiches to superlattices; Δρ/ρ is approximately 50% in a superlattice with r=5 ML, which is an order of magnitude larger than in a superlattice with r=1 ML. In a sandwich the difference between r=5 and r=1 is closer to a factor of 5. In the sandwiches Δρ/ρ is smaller for n=0.131 than for n=1.05.

Theory of the magnetoresistance in magnetic multilayers: Analytical expressions from a semiclassical approach.

We use the semiclassical approach of Camley and Barnas to derive analytical expressions for the giant magnetoresistance of magnetic multilayers in several simple cases. We discuss the main features of our results and apply our expressions of the magnetoresistance to the interpretation of experimental data on Fe/Cr and Co/Ru multilayers. Finally we compare our results with those obtained in quantum models.

Exchange interactions and giant magnetoresistance in magnetic multilayers

Abstract Magnetic layer structures consisting of alternating magnetic and non-magnetic layers exhibit new magnetic phenomena with great potential for applications in magnetic storage technology. It is found experimentally that the magnetic moments of neighbouring magnetic layers are spontaneously aligned ferromagnetically or antiferromagnetically depending on the thickness of the intervening nonmagnetic layers. This implies an oscillatory magnetic coupling between the layers mediated by the nonmagnetic spacer layers. The resistance of the structure when a current is passed in the direction parallel to the layers is much higher in the antiferromagnetic configuration than in the ferromagnetic one. The magnetic configuration of the layers, and hence the resistance of the structure, is strongly influenced by an applied magnetic field. This effect, called giant magnetoresistance, can be exploited to read information from a magnetic disc. The purpose of this review is to introduce the reader to magnetic multilayers and to explain the underlying physical mechanisms that cause the oscillatory coupling and giant magnetoresistance.