Magnetic excitations in a nanocontact

The domain wall in a ferromagnetic nanocontact adopts a specific configuration---N\'eel-like, vortex, or Bloch-like---depending on the dipole-dipole interactions governed by the size and shape of the contact and its atomic structure. Spontaneous thermal fluctuations between these modes arise in a soft ferromagnet at room temperature when the dimensions of the contact are less than about 10 nm. The giant magnetoresistance of a nanocontact may be reduced, but not eliminated by the mode fluctuations.