Angular dependence of characteristic fields in spin-valves

Spin-valves are commonly characterised by a series of representative field values such as the coercivity of the magnetic layers, the exchange bias field and the interlayer coupling field. As the angle of an applied field is varied, these values have been observed to vary as periodic functions containing many high order harmonic terms. We analyse the magnetic behaviour of a spin-valve in terms of an extended Stoner-Wohlfarth model, and show that only the fundamental terms are necessary in the free energy of the system for these complex angular dependences to arise. We present illustrative data for spin-valve multilayer films. The complex angular dependences are seen to arise when the unidirectional and uniaxial energy terms are of comparable size, as in the free layer of a weakly coupled spin-valve. (C) 2000 Elsevier Science S.A. All rights reserved.