Direct Observation of a Localized Magnetic Soliton in a Spin-Transfer Nanocontact

We report the direct observation of a localized magnetic soliton in a spin-transfer nanocontact using scanning transmission x-ray microscopy. Experiments are conducted on a lithographically defined 150 nm diameter nanocontact to an ultrathin ferromagnetic multilayer with perpendicular magnetic anisotropy. Element-resolved x-ray magnetic circular dichroism images show an abrupt onset of a magnetic soliton excitation localized beneath the nanocontact at a threshold current. However, the amplitude of the excitation similar or equal to 25 degrees at the contact center is far less than that predicted (<= 180 degrees), showing that the spin dynamics is not described by existing models.