Thin film Co:TiO2 photo

A representation of a thin film of Co:TiO2 in which ferromagnetism arises because titanium 3d electrons (green) travel around the material aligning the spin of cobalt atoms (pink) so that they all point in the same direction.

The blue and brown spheres correspond to titanium and oxygen atoms, respectively.

Credit: 2011 Takumi Ohtsuki