via ferroelectric Polarization Control*

In this study, we use epitaxial Pb(Zr,Ti)O₃ (PZT)/ La_0.8Sr_0.2MnO₃ (LSMO) heterostructures as a model system to decouple the effects of epitaxial strain and charge doping on the magnetocrystalline anisotropy (MCA) in LSMO. By switching the polarization of PZT, we have achieved nonvolatile modulation of the biaxial in-plane magnetic anisotropy in LSMO, as revealed by planar Hall effect studies. The magnetic anisotropy energy (MAE) in the hole accumulation state is enhanced by about 22% compared to the depletion state, in quantitative agreement with the DFT calculations. In contrast, the MAE extracted in chemically doped LSMO films is significantly lower than the theoretical prediction, clearly illustrating the difference between the electric field effect doping and chemical substitution. The discrepancy has been attributed to the different lattice parameters for bulk LSMO at these compositions, where the higher doping sample is subjected to a larger tensile strain on SrTiO₃ substrates, concomitantly lowering the MCA. Our result provides the first combined experimental and theoretical study that unambiguously identifies the role of charge doping in determining the MCA in LSMO.