Electric-field modulation of exchange stiffness in MgO/CoFeB with   perpendicular anisotropy
  We observe magnetic domain structures of MgO/CoFeB with a perpendicular magnetic easy axis under an electric field. The domain structure shows a maze pattern with electric-field dependent isotropic period. We find that the electric-field modulation of the period is explained by considering the electric-field modulation of the exchange stiffness constant in addition to the known magnetic anisotropy modulation. 
T. Dohi, S. Kanai, A. Okada, F. Matsukura, and H. Ohno
cond-mat.mtrl-sci