Spin-Wave Resonances Affected by Skin-Effect in Conducting Magnetic Nanowire Arrays at Terahertz Frequencies

The properties of localized standing spin wave (SW) resonances are investigated numerically for a regular 2-D array of 10 nm diameter, 300 nm long metallic (iron) nanowires, magnetized at different orientations of the bias magnetic field mmb H0 with respect to the wire axis. At 30 THz the penetration depth of the electromagnetic (EM) waves can be close to the diameter of the nanowires, leading to interesting resonance effects as a result of the inhomogeneous rf magnetization distribution across the nanowire diameter. The mathematical model considers the metallic character of the wires and the exchange interactions between the wires, when solving Maxwell equations simultaneously with the Landau-Lifshitz equation for the magnetization. The transmission coefficients |T₂₁| of TEM waves through arrays with different wire radius were determined. There are well-defined extrema of |T₂₁| at certain values of the bias magnetic field mmb H0, corresponding to ferromagnetic resonance (FMR) and antiresonance (FMAR) modes. The position of these maxima and minima does not depend on the orientation of H0, although |T₂₁| is sensitive to the direction of mmb H0. The distribution of the rf magnetization component across the nanowire is calculated for the second and low order exchange SW modes.