Peter GRUENBERG

Institut fur Festkorperforschung, Forschungszentrum Julich GmbH, Germany

Title: Spinpolarisation: from the EPR paradox to coupling and Giant Magnetoresistance in layered magnetic structures

The discovery of spatial quantization of spins in a magnetic field by Stern and Gerlach (SG) in 1922 is one of the basic experiments for our understanding of quantum mechanics. In this lecture I want to discuss first a thought experiment designed by Einstein Podolsky and Rosen (EPR) using the principle of the SG-experiment as suggested by Bohm in order to test Heisenberg's uncertainty principle. For practical reasons this experiment could never be realized however new experiments started by Aspect and by Zeilinger using polarized light and comparison with Bell's inequality relation support the uncertainty principle.

In the second part of the lecture I will discuss the effect of the spatial quantization on various magnetic properties, in particular interlayer exchange coupling (IEC), Giant Magnetoresistance (GMR) and tunnel magnetoresistance (TMR) in layered magnetic structures.

In GMR magnetic alignment in these layered structures has an effect on electrical resistivity. There is also an inverse effect to this called "Current Induced Magnetic Switching" where spinpolarized currents have an impact on magnetic order. In this lecture emphasis will generally be laid on a basic physical understanding of the phenomena.