Spintronic devices currently rely on magnetic switching or controlled motion of domain walls by an external magnetic field or spin-polarized current. Achieving the same degree of magnetic controllability using an electric field has potential advantages including enhanced functionality and low power consumption. Here we report on an approach to electrically control local magnetic properties, including the writing and erasure of regular ferromagnetic domain patterns and the motion of magnetic domain walls, in CoFe-BaTiO3 heterostructures. Our method is based on recurrent strain transfer from ferroelastic domains in ferroelectric media to continuous magnetostrictive films with negligible magnetocrystalline anisotropy. Optical polarization microscopy of both ferromagnetic and ferroelectric domain structures reveals that domain correlations and strong inter-ferroic domain wall pinning persist in an applied electric field. This leads to an unprecedented electric controllability over the ferromagnetic microstructure, an accomplishment that produces giant magnetoelectric coupling effects and opens the way to electric-field driven spintronics.

The directions of the arrows in the ferroelectric domain image (FE) of Figure 2 in the above-mentioned article are incorrect and should be rotated by 90° so that they reflect the experimentally observed collinear alignment between the ferroelectric polarization of the BaTiO 3 substrate and the strain-induced uniaxial magnetic easy axes of the CoFe film. We provide the corrected Figure 2 below. The arguments and conclusions of the original article are not affected. Figure 2.Magnetic hysteresis curve and polarization microscopy images of the ferroelectric domain structure (FE) and magnetic stripe pattern during several stages of the magnetization reversal process (R1, S1, R2, S2). The figure depicts experimental data for a magnetic field angle of θ = 10°. The hysteresis curve represents an average magnetic response from many a1 and a2 domains. The arrows in the images indicate the orientation of ferroelectric polarization (FE) and film magnetization in the remnant state (R1 and R2) and during abrupt magnetic switching (S1 and S2). The imaged areas are 30 × 40 µm. CORRECTION

We report on domain formation and magnetization reversal in epitaxial Fe films on ferroelectric BaTiO3 substrates with ferroelastic a − c stripe domains. The Fe films exhibit biaxial magnetic anisotropy on top of c domains with out-of-plane polarization, whereas the in-plane lattice elongation of a domains induces uniaxial magnetoelastic anisotropy via inverse magnetostriction. The strong modulation of magnetic anisotropy symmetry results in full imprinting of the a − c domain pattern in the Fe films. Exchange and magnetostatic interactions between neighboring magnetic stripes further influence magnetization reversal and pattern formation within the a and c domains.Ferromagnetic pattern formation via efficient coupling to ferroelectric domain structures has recently been demonstrated. 1-6 Direct correlations between ferromagnetic and ferroelectric domains and its persistence during ferroelectric polarization reversal open up promising ways for electric-field control of local magnetic switching 1-5 and the motion of magnetic domain walls. 6 In systems based on interlayer strain transfer, the ferroelastic domain structure of a ferroelectric material induces local magnetoelastic anisotropies in a ferromagnetic film via inverse magnetostriction. Within the ferromagnetic sub-system, the magnetoelastic anisotropy competes with intrinsic magnetic properties including magnetocrystalline anisotropy and exchange and magnetostatic interactions between domains. Consequently, the evolution of the magnetic microstructure in an applied magnetic or electric field depends critically on the two ferroic materials, the ferromagnetic layer thickness, and the ferroelastic domain size.

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This paper reports on the temperature evolution of local elastic interactions between ferromagnetic CoFe films and ferroelectric BaTiO3 substrates. Polarization microscopy measurements indicate that growth-induced stripe domains in the CoFe films are preserved and strengthened during cooling and heating through the structural phase transitions of BaTiO3. Moreover, rotation of the magnetic easy axes at the tertragonal-to-orthorhombic transition (T = 278 K) and at T ≈ 380 K simultaneously switches the local magnetization of both uniaxial domains by 90 • . Irreversible changes in the ferromagnetic domain pattern are induced when the room-temperature ferroelectric domain structure is altered after temperature cycling.

Spin dynamics controlled by magnetoelastic coupling and applied electric fields might play a vital role in future developments of magnonics, i.e., the exploitation of spin waves for the transmission and processing of information.We have performed broadband spin-wave spectroscopy on a magnetostrictive CoFeB alloy grown on a ferrolectric BaTiO 3 substrate causing elastic strain with a quasi-periodic modulation. We find characteristic eigenfrequencies and spin-wave modes with large group velocities and small damping. These results suggest bright perspectives for electric-field control of reprogrammable magnonics.

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