Reduction of In-Plane Uniaxial Magnetic Anisotropy in Patterned Single-Crystal Fe Dot Arrays

Single-crystal Fe dot arrays with the lateral size varying from 400 nm to 50 nm are fabricated by focused ion beam (FIB) direct writing from a single-crystalline 10 monolayer (ML) Fe (100) continuous thin film grown on GaAs substrate. The Kerr hysteresis loops of both dot arrays and continuous thin film are measured by focused magnetooptical Kerr effect (MOKE) measurements along four major crystal directions: [0-11] [010] [011] and [001]. It is found that the in-plane uniaxial anisotropy has been greatly reduced down to zero in the dot arrays when the size is less than 150 nm. The micromagnetic simulations confirm the reduction of this intrinsic in-plane uniaxial anisotropy in the patterned dots by separating the effect of the shape anisotropy. The experimental and simulation results further indicate an additional magnetic uniaxial anisotropy along the [010] direction.