Angular dependence of the perpendicular giant magnetoresistance of multilayers

We present measurements of the angular dependence of the giant magnetoresistance in multilayers with the current applied perpendicular to the layer plane. The samples used are (Ni80Fe20/Ag/Co/Ag) multilayers sandwiched between superconducting underlayers and overlayers. The angle between the magnetizations of the Ni80Fe20 and Co layers is continuously varied. We find that the current-perpendicular-to-the-plane magnetoresistance of these multilayers varies as 1-a cos(2)(theta/2)+b cos(4)(theta/2), where theta is the angle between the magnetization of successive magnetic layers and bla is between 0.1 and 0.3. We discuss the theoretical interpretation of this variation.