Fabrication of ordered arrays of permalloy submicrometric dots

Nanometric permalloy dots have been fabricated on silicon substrates by electron beam lithography combined with a lift-off technique. The SEM images show regular and circular dots with typical diameter of 250 nm. The dots have been arranged in ordered square arrays with a spacing of 400 nm, and cover a fetal area of 0.8 x 0.8mm(2). This large area allows direct SQID magnetometer measurements to study the magnetic properties of these submicrometric structures, which is important to understand the different pinning mechanisms of magnetic dots on superconducting films. It has been observed that in the usual conditions where pinning effect are present, low-range-field range and H perpendicular to the substrate, the hysteresis loop shows low values of magnetization. (C) 1999 Elsevier Science B.V. All rights reserved.