Magnetization pattern of ferromagnetic nanodisks

We explore the magnetization pattern of Co and permalloy disks with diameters between 80 nm and 1 mu m by using two complementary experimental techniques: Lorentz microscopy and magnetic force microscopy (MFM). By means of Lorentz microscopy we show that the dominating magnetization pattern of the disks is a vortex structure with closed flux lines in the plane of the disks. Complementary MFM measurements demonstrate that the magnetization in the center of the disks is tilted out of the plane of the disk. The experimental findings closely agree with corresponding micromagnetic calculations. (C) 2000 American Institute of Physics. [S0021-8979(00)02519-6].