On the strain coupling across vertical interfaces of switchable BiFeO3–CoFe2O4 multiferroic nanostructures

In magnetoelectrically coupled CoFe2O4–BiFeO3 nanostructures vertical and lateral lattice parameters of both phases are determined. We find that the in-plane lattice parameter of CoFe2O4 is fully relaxed whereas it presents compressive strain along the out-of-plane direction. Although the CoFe2O4–BiFeO3 interface is semicoherent, CoFe2O4 out-of-plane lattice strain is not relaxed after selective removal of the matrix and thus it is of nonelastic origin. In spite of the absence of elastic residual strain caused by CoFe2O4–BiFeO3 interfaces, the two phases are mechanically coupled as demonstrated by the electrical switching of the magnetization.