Ferroelectric polarization switching induced charge versus strain mediated interfacial magnetic phases in oxide heterostructures*

We studied ME coupling at La0.67Sr0.33MnO3/PbZr0.2Ti0.8O3 interface on STO (001) substrate as a function of polarization direction on PZT layer with combined results from polarized neutron reflectometry (PNR) experiments and DFT calculations. PNR results show antiferromagnetic (AFM) phases on few unit cells of ferromagnetic (FM) LSMO at the interface for polarization directions away from the sample interface due to self- and negatively polarized PZT.  However, interface remains ferromagnetic for positive polarization. Furthermore, there is increase in bulk LSMO magnetization while going from positive, self to negative polarization directions. To find the origin of such ME coupling is either charge or strain mediated, magnetic phase evolution as a function of strains is studied from DFT calculations for both polarization. For negative polarization, both A-AFM and FM phases exist for zero strain and A-AFM and FM phases start to dominate with increasing negative and positive strain respectively. The magnetic moments are significantly dropped within few unit cells of LSMO interface for negative and intact for positive polarization, which purports the results from PNR .