Abstract
We utilize polarized neutron reflectometry (PNR) in consort with ab initio based density functional theory (DFT) calculations to study magnetoelectric coupling at the interface of a ferroelectric PbZr0.2Ti0.8O3 (PZT) and magnetic La0.67Sr0.33MnO3 (LSMO) heterostructure grown on a Nb-doped SrTiO3 (001) substrate. Functional device working conditions are mimicked by gating the heterostructure with a Pt top electrode to apply an external electric field, which alters the magnitude and switches the direction of the ferroelectric (FE) polarization, across the PZT layer. PNR results show that the gated PZT/LSMO exhibits interfacial magnetic phase modulation attributed to ferromagnetic (FM) to A-antiferromagnetic (A-AF) phase transitions resulting from hole accumulation. When the net FE polarization points towards the interface (positive), the interface doesn't undergo a magnetic phase transition and retains its global FM ordered state. In addition to changes in the interfacial magnetic ordering, the global magnetization of LSMO increases while switching the polarization from positive to negative and decreases vice versa. DFT calculations indicate that this enhanced magnetization also correlates with an out of plane tensile strain, whereas the suppressed magnetization for positive polarization is attributed to out of plane compressive strain. These calculations also show the coexistence of FM and A-AF phases at zero out of plane strain. Charge modulations throughout the LSMO layer appear to be unaffected by strain, suggesting that these charge mediated effects do not significantly change the global magnetization. Our PNR results and DFT calculations are in consort to verify that the interfacial magnetic modulations are due to co-action of strain and charge mediated effects with the strain and charge effects dominant at different length scale.
| Original language | English |
|---|---|
| Pages (from-to) | 13033-13041 |
| Number of pages | 9 |
| Journal | RSC Advances |
| Volume | 9 |
| Issue number | 23 |
| DOIs | |
| State | Published - 2019 |
Funding
This research was supported by the DoD Air Force Office of Scientic Research (AFOSR) under award No FA9550-18-1-0196. Prof. E. Fohtung also acknowledges partial support for the LANSCE Professorship sponsored under Triad National Security, LLC through the New Mexico Consortium under subcontract No 350. The research conducted at the Spallation Neutron Source was sponsored by the Scientic User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. The work at Los Alamos National Laboratory was supported in part by the NNSA's Laboratory Directed Research and Development Program and was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy Office of Science. Los Alamos National Laboratory, an affirmative action equal opportunity employer, is managed by Triad National Security, LLC for the U.S. Department of Energy's NNSA, under contract 89233218CNA000001.