Study of exchange field and coercivity in hysteresis loop measurements with out-of-plane applied fields

We study the angular dependence of the exchange field and the coercivity of an in-plane exchange biased system in hysteresis loop measurements with the field applied out of the film plane by a Stoner–Wohlfarth model where the coherent rotation of the magnetization is assumed. The model shows an overall 1/cosψ dependence of both the exchange field and the coercivity, where ψ is the angle the applied field makes with the film plane. However, when ψ is close to 90°, the exchange field and the coercivity deviate from the 1/cosψ function. The coercivity in particular goes to zero when ψ approaches 90°. The principle and methodology of the model can also apply to other magnetic systems where the coercivity displays similar angular behaviour.