Structure and Magnetism of LSMO/BTO/MgO/LSMO Multilayers

A multiferroic tunnel junction (MFTJ) is a promising device for future memory systems with discrete and different logic states which are controlled by a combination of electric and magnetic fields. The goal of ongoing research is to present ferroelectric and ferromagnetic properties, especially at room temperature (RT), represented as high values of tunnel electroresistance (TER) and tunnel magnetoresistance (TMR). A key aspect is the appropriate preparation of a sample allowing epitaxial growth. The thin layers were prepared by pulsed laser deposition on atomically smooth monocrystalline SrTiO₃ (STO) substrates. The ferromagnetic metal layers La_{0.67}Sr_{0.33}MnO₃ (LSMO) are separated by a layer of a ferroelectric insulator - BaTiO₃ (BTO). The same structure of LSMO, BTO and STO (perovskite) and a similar lattice constant make it possible to obtain high-quality heterostructures. Magnetic measurements confirm differences in the magnetic coercivity of the top and bottom LSMO layer, which allows to obtain their parallel and antiparallel magnetization orientation. A modification of the interfaces of BTO by thin MgO layer enables an increase in the value of the TER effect.