Magnetic coupling phenomena in EuS/Pb thin film double layers

The magnetic properties of EuS/Pb double layers (a ferromagnetic insulator on a superconducting metal) were investigated by means of 50 Hz hysteresis. The magnetic coupling between the two layers does not set in spontaneously. Two procedures for achieving magnetic coupling are described: first, by means of a d.c. magnetic field perpendicular to the film plane; secondly, with an a.c. field in the film plane. The coupled states are characterized by a slowing of the 50 Hz magnetization reversals. The degree of slow-down depends on the strength of the magnetic coupling.