Single-Domain Circular Nanomagnets

The magnetic properties of deep submicron circular nanomagnets fabricated by high-resolution electron beam lithography from Supermalloy $({\mathrm{Ni}}_{80}{\mathrm{Fe}}_{14}{\mathrm{Mo}}_{5})$ have been studied as a function of both diameter (500--55 nm) and thickness (6--15 nm). A high sensitivity magneto-optical method has been used to measure the hysteresis loops of these nanomagnets. An experimental phase diagram in diameter and thickness has thus been produced which identifies a vortex phase and a single-domain phase. The two phases agree well with micromagnetic theory.