Shape effect on the negative equivalent permeabilities of chevronic thin films of silver

In this work, the chevronic films composed of silver nanorods are fabricated using glancing angle deposition (GLAD). The chevronic structure is grown by bidepositing opposite nanorods sequentially: the substrate is oriented at the polar angle φ=0 deg (about the substrate"s normal) for the bottom rods and φ=180 deg for the top rods. When the applied electric field is parallel to the plane φ=0 deg, the induced magnetic dipole moment between nanorods leads to a negative real part of the equivalent permeability. The equivalent refractive indices, the equivalent permittivities and the equivalent permeabilities of chevronic films with thickness 230 ± 5 nm for p-polarized light are measured by walk-off interferometer. The equivalent permeabilities of chevronic films with lengths of top rods 291 nm, 409 and 509 nm and bottom rods 512 nm, 378 nm and 301 nm are measured to be -2.406+0.443 i, -3.870+2.109 i and -2.126+0.904 i at the wavelength of 639 nm, respectively. The shape affects the real part of the equivalent permeability significantly. When the length of the top rods is longer than that of the bottom rods, the magnetic dipole moment between nanorods is suppressed and the quantity of the equivalent permeability becomes small. The real part of equivalent permeability of the chevronic film is related to the lengths of top and bottom nanorods.