Angular dependence of the exchange coupling in a NiFe/CoO bilayer him
has been measured, revealing different symmetry for the exchange field
H-E and the coercivity H-C. The exchange held exhibits unidirectional
symmetry with a more complex dependence than a simple cosine. The pro
posed free energy accounts for the experimental results. (C) 1998 Else
vier Science B.V. All rights reserved.