Engineered magnetization and exchange stiffness in direct-write Co-Fe nanoelements
Abstract
Media with engineered magnetization are essential building blocks in superconductivity, magnetism and magnon spintronics. However, the established thin-film and lithographic techniques insufficiently suit the realization of planar components with on-demand-tailored magnetization in the lateral dimension. Here, we demonstrate the engineering of the magnetic properties of CoFe-based nanodisks fabricated by the mask-less technique of focused electron beam induced deposition (FEBID). The material composition in the nanodisks is tuned in-situ via the e-beam waiting time in the FEBID process and their post-growth irradiation with Ga ions. The magnetization Ms and exchange stiffness A of the disks are deduced from perpendicular ferromagnetic resonance measurements. The achieved Ms variation in the broad range from 720 emu/cm3 to 1430 emu/cm3 continuously bridges the gap between the Ms values of such widely used magnonic materials as permalloy and CoFeB. The presented approach paves a way towards nanoscale 2D and 3D systems with controllable and space-varied magnetic properties.