Magnetic bubbles in FePt nanodots with perpendicular anisotropy

We present experimental evidence, by magnetic force microscopy, for the existence of magnetic bubbles in suitably designed high-quality circular FePt nanodots. We specifically study dots of sizes where this fundamental magnetic state is a ground state and it is spontaneously created. We also observe triple-domain states consisting of concentric rings with alternating magnetization. A numerical study confirms the range of stability of the observed magnetic states and predicts the phase diagram in parameter space. Differences in the topology of these states imply distinct dynamical behavior, providing the basis for fundamental dynamical studies.