Three-dimensional magnetization needle arrays with controllable orientation.

Abstract

Based on the Richards-Wolf vectorial diffraction theory and inverse Faraday effect, we first propose a scheme to generate three-dimensional magnetization needle (MN) arrays with arbitrary orientation for each individual needle and controllable spatial position and number by reversing the electric dipole array radiation. To achieve this, each unit of the electric dipole array has two electric dipoles with orthogonal oscillation directions and quadrature phase and is located mirror-symmetric with respect to the focal plane of the high numerical aperture lens. Uniformly distributed MNs with a subwavelength lateral size of 0.44λ and a longitudinal depth of 5.36λ with four different orientations are obtained by optimized arrangement for 2N (here, N=2) units of the electric dipole array. The corresponding purity of MNs is also discussed in detail. Furthermore, two combinations of MN arrays with orthogonal orientation are emphatically exploited in the hybrid bit-patterned media recording. The results illustrate the richness of the proposed methods to locally control the particular orientation properties of the MN and find many potential applications in multichannel/multilayer magneto-optical storage, information security, and spintronics.