Dependence of Magnetoresistance and Superconducting Transition Temperature on Relative Orientation of Magnetization Easy Axis to Current Direction in a Py/Nb/Py Trilayer

The magnetoresistance (MR) and the superconducting transition temperature T _c as well as the longitudinal and the transverse magnetic moments are studied in order to find an underlying cause for the inverse spin switch behavior of bare Py/Nb/Py trilayers. Our measurements consistently show that the increase of MR and the decrease of T _c in the case of the antiparallel alignment between the magnetizations of the two Py layers (AP state) compared to those in the parallel alignment (P state), which is known as the inverse spin switch behavior, are largely due to stray field from the domain walls in the domain state that occurs during the AP state. The influence of stray field on the MR and the T _c shift between the AP and P state is measured in the bridges with each axis oriented at various angles phi with respect to the magnetization easy axis. With increasing phi from 0deg to 90deg, T _c shift between the AP and P state is almost constant around 5 mK up to phi = 54deg, then becomes 11 mK when phi = 72deg, but is reduced to 2 mK for phi = 90deg . In addition, the effect by the stray field not originating in the domain walls is observed outside the domain states in the MR and in the transverse magnetic moment measurements.