Fabrication of ordered arrays of permalloy submicrometric dots

Nanometric permalloy dots have been fabricated on silicon substrates by ele ctron beam lithography combined with a lift-off technique. The SEM images s how regular and circular dots with typical diameter of 250 nm. The dots hav e been arranged in ordered square arrays with a spacing of 400 nm, and cove r a fetal area of 0.8 x 0.8mm(2). This large area allows direct SQID magnet ometer measurements to study the magnetic properties of these submicrometri c structures, which is important to understand the different pinning mechan isms of magnetic dots on superconducting films. It has been observed that i n the usual conditions where pinning effect are present, low-range-field ra nge and H perpendicular to the substrate, the hysteresis loop shows low val ues of magnetization. (C) 1999 Elsevier Science B.V. All rights reserved.