Magnetoelectric coupling in BaTiO3 / CaMnO3 thin film heterostructures

SOLANGE DI NAPOLI; MARÍA ANDREA BARRAL; AGUSTÍN LÓPEZ PEDROSO; LAURA STEREN; MYRIAM AGUIRRE; ANA MARÍA LLOIS

Uppsala

Conferencia; Joint European Magnetic Symposia 2019; 2019

One route towards the development of multiferroic materials with strong magnetoelectric coupling is byexploring the break of time reversal and space inversion symmetries that occur at the interface betweena magnetic and a ferroelectric material. The properties of each component of the heterostructures canbe chosen within a large number of materials, allowing a better optimization of the desired properties.This engineered magnetoelectric coupling could reach values that are orders of magnitude larger thanthose typical of single phase multiferroics.In this work the structural, electronic and magnetic properties of BaTiO3/CaMnO3 heterostructuresgrown on an SrTiO3 substrate are investigated from first principles calculations. The most importanteffects to take into account when dealing with the electronic and magnetic properties of thin films offerroelectric / magnetic heterostructures can be mechanical strain, charge transfer and interface effects.As a first step, we study how the confinement and the epitaxial tensile strain induced by an SrTiO3substrate affect the magnetic properties of CaMnO3 thin films for both, MnO2- and CaO-terminatedsurfaces. We find that when the film is CaO-terminated the magnetic structure remains equal to the bulkone (antiferromagnetic coupling between Mn nearest neighbours, i.e. GAF) whereas a MnO2-terminatedfilm favors an in-plane ferromagnetic coupling between Mn atoms. These results are contrasted with theobtained experimental results.Finally, we also analyze the influence of the BaTiO3 polarization switching by means of the chargetransfer through the interface for different interface combinations, namely BaO-MnO2 and TiO2-CaO