  We use spin-resolved electron tunneling to study the exchange field in the Al
component of EuS/Al bilayers, in both the superconducting and normal-state
phases of the Al. Contrary to expectation, we show that the exchange field,
Hex, is a non-linear function of applied field, even in applied fields that are
well beyond the EuS coercive field. Furthermore the magnitude Hex is unaffected
by the superconducting phase. In addition, Hex decreases significantly with
increasing temperature in the temperature range of 0.1-1 K. We discuss these
results in the context of recent theories of generalized spin-dependent
boundary conditions at a superconductor/ferromagnet interface.
