Measurement of magnetic anisotropyby ferromagnetic resonance

The effective magnetic field caused by exchange coupling between a ferromagnetic and an antiferromagnetic bilayer and its magnetic anisotropy have been investigated by means of ferromagnetic resonance. It was shown that the exchange bias phenomenon occurrence and its positive or negative characteristic for ferromagnetic/antiferromagnetic bilayer can be identified from its magnetic resonance spectrum. In addition, when the field was applied along different crystalline directions, the behavior of magnetic resonance field will be changed, and is closely dependent on the magnetocrystalline anisotropy and unidirectional anisotropy induced by the interface coupling in ferromagnetic/antiferromagnetic bilayer. Anomalies in the ferromagnetic resonance frequency studied as functions of applied field, including its orientation and strength, are interpreted as evidence for the four fold anisotropy and unidirectional anisotropy. Our conclusions are in good agreement with the related experiments.