Dynamic and rotatable exchange anisotropy in Fe/KNiF3/FeF2trilayers

Results from ferromagnetic resonance experiments carried out on epitaxially grown Fe/KNiF<sub>3</sub>/FeF<sub>2</sub> trilayers are presented. Exchange coupling between the KNiF<sub>3</sub>, a weak anisotropy antiferromagnet, and the Fe leads to shifts in the resonance field of the ferromagnet. The field shifts can be described by a temperature-dependent exchange anisotropy &H_{{rm dyn}}^{{rm AFM}} ;. &H_{{rm dyn}}^{{rm AFM}} ; depends on the orientation direction of the applied field relative to the magnetic anisotropy axis, and a non-monotonic dependence on KNiF<sub>3</sub> thickness. Three thickness regimes appear that correspond to different values of exchange bias in each region. A qualitative understanding of the basis for these three thickness regimes due to spin canting at the interfaces is presented. Our results illustrate a method to tune the value of exchange anisotropy using a combination of different antiferromagnets