Ferromagnetic Resonance study of sputtered Ru(7 nm)/NiFe(t FM)/IrMn(6 nm)/Ru(5 nm) exchange-biased bilayers at X and Q-band microwave frequencies reveals the excitation of spin-wave and NiFe resonance modes. Angular variations of the in-plane resonance fields of spin-wave and NiFe resonance modes show the effect of the unidirectional anisotropy, which is about twice larger for the spin-wave mode due to spin pinning at the NiFe/IrMn interface. At Q-band frequency the angular variations of in-plane resonance fields also reveal the symmetry of a uniaxial anisotropy. A modified theoretical model which also includes the contribution of a rotatable anisotropy provides a good description of the experimental results.
Bibliographical noteFunding Information:
This work was partially supported by the Brazilian agencies CNPq (throughout the Projects 141830/2009-3 and 151440/2013-1 ), FAPERJ and CAPES.
- Exchange bias
- Ferromagnetic resonance
- Magnetic bilayers
- Spin pinning
- Spin wave resonance