Possible existence of a new type of left-handed materials in coupled ferromagnetic bilayer films

On the basis of Landau–Lifshitz–Gilbert (LLG) equation, an anomalous ferromagnetic resonance behavior is demonstrated in detail. Coupling between the magnetic moments produces a 3π  /2 phase delay for one of the moments ferromagnetic resonance unusually, thus leads the sign of magnetic susceptibility χ˜=χ′-jχ″ to be opposite to that induced by the usual ferromagnetic resonance. Consequently, a left-handed material (LHM) may be formed near the low-frequency side of the resonance. Particularly, a LHM with negative value of real part of permeability only is predicted.