Preparation of magnonic crystals with nanoislands by focused ion beam etching

This paper describes the patterning of gold, cobalt, nickel, cobalt-gold, and nickel-gold nanofilms on the surface of epitaxial garnet ferrite films through sputtering with a focused gallium ion beam. We show that the minimum size and spacing of regularly shaped metallic islands depend not only on the gallium ion beam spot size but also on the thickness of the metallic film. Using Au and Co-Au films less than 10 nm thick as an example, we have demonstrated for the first time the possibility of producing a periodic structure in the form of rectangular metallic islands 70 nm or less in lateral dimensions. Such structures are potentially attractive as two-dimensional magnonic crystals.