Electric field induced magnetic anisotropy in a ferromagnet.

We report the first observation of a transient all electric field induced magnetic anisotropy in a thin film metallic ferromagnet. We generate the anisotropy with a strong (approximately 10(9) V/m) and short (70 fs) E-->-field pulse. This field is large enough to distort the valence charge distribution in the metal, yet its duration is too brief to change the atomic positions. This pure electronic structure alteration of the sample generates a new type of transient anisotropy axis and strongly influences the magnetization dynamics. The successful creation of such an anisotropy opens the possibility for all E-->-field induced magnetization reversal in thin metallic films--a greatly desired yet unachieved process.