Transition metal oxides display a wide range of functional properties that are sensitive to distortions of the crystal lattice. Epitaxial films of these materials are widely studied for use in devices, and have been transferred to various substrates on which they cannot grow. However, they have not previously been transferred to substrates that deform in response to a voltage.
We used pulsed laser deposition to epitaxially grow a ferromagnetic perovskite oxide of manganese (La0.7Sr0.3MnO3) on a well-matched substrate (SrTiO3) via a sacrificial layer (SrRuO3). After chemically etching the sacrificial layer, the magnetic film was transferred to an electroactive substrate of PMN-PT [0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3]. The release is known as epitaxial lift-off, and the transfer represents a form of van der Waals integration.
The film magnetization was much larger than it would have been if the film had been grown directly on PMN-PT, and film magnetization could be substantially modified via strain by applying a voltage between the film and a PMN-PT back electrode. These electrically driven magnetic changes were just as strong as they would be across an epitaxial interface, possibly due to the serendipitous formation of an amorphous interfacial layer during the etch.
Images obtained at Diamond Light Source (UK) revealed that the magnetic changes arose due to the rotation of magnetic domains, whose perimeters were determined by cracks. A wide range of rotation angles was attributed to a spatially varying stress associated with these cracks.
In future, the physical and chemical properties of any epitaxially grown film could likewise be electrically controlled via strain, paving the way towards device applications.
Figure caption: Magnetic vector maps at the A and B states of electrical remanence. Colours identify directions of magnetization, field of view ~ 20 µm, resolution ~ 50 nm. Each map combines two photoemission electron microscopy (PEEM) images that were obtained at Diamond Light Source. The PEEM images for each map were obtained for sample azimuthal angles that differed by 90°. X-ray circular magnetic dichroism (XMCD) provided the contrast in each PEEM image.
D. Pesquera, E. Khestanova, M. Ghidini, S. Zhang, A. P. Rooney, F. Maccherozzi, P. Riego, S. Farokhipoor, J. Kim, X. Moya, M. E. Vickers, N. A. Stelmashenko, S. J. Haigh, S. S. Dhesi and N. D. Mathur, “Large magnetoelectric coupling in multiferroic oxide heterostructures assembled via epitaxial lift off”, Nature Communications 11, 3190 (2020)
