Electronic and Magnetic Properties of Lanthanum and Strontium Doped Bismuth Ferrite: A First-Principles Study

Ayana Ghosh,S M Nakhmanson,S Pamir Alpay,Jian-Xin Zhu,Hongchul Choi,Dennis P Trujillo

doi:10.1038/s41598-018-37339-3

Abstract

While bismuth ferrite BiFeO3 (BFO) is a well studied multiferroic material, its electronic and magnetic properties in the presence of A-site dopants have not been explored widely. Here we report the results of a systematic study of the local electronic structure, spontaneous polarization, and magnetic properties of lanthanum (La) and strontium (Sr) doped rhombohedral bismuth ferrite within density functional theory. An enhanced ferroelectric polarization of 122.43 μC/cm2 is predicted in the uniformly doped BiLaFe2O6. We find that substitution of Sr in the A-site drives the system into a metallic state. The nature of magnetism arises mainly from the B-site Fe exhibiting a G-type antiferromagnetic ordering. Our study finds that upon dopant substitution, the local magnetic moment is decreased and its magnitude is dependent on the distance between the Fe and the dopant atom. The correlation between the local moment and the distance between the Fe and the dopant atom is discussed.

Highlights

Recent research to enhance electronic and magnetic properties of BFO has shown that the presence of common A-site dopants such as La and Sr can have a significant effect on decreasing leakage current in BFO thin films[15,16,17,18,19,20,21,22,23]
II briefly reviews the computational details of formulating structural optimization, calculations of magnetic moment and spontaneous polarization using the Berry phase method of various supercells within first-principles theory
We have systematically studied the band gap for Ueff = 0, 2, 4 and 6 eV with the generalized gradient approximation (GGA) exchange-correlation functional for the pristine BFO in primitive unit cell and obtained values of 1.0 eV, 2.2 eV, 2.5 eV and 3.2 eV respectively

Summary

Introduction

Recent research to enhance electronic and magnetic properties of BFO has shown that the presence of common A-site dopants such as La and Sr can have a significant effect on decreasing leakage current in BFO thin films[15,16,17,18,19,20,21,22,23]. Improving the antiferromagnetic ordering along with retaining high spontaneous polarization of BFO through judicious doping to make it technologically more feasible has captured much interest in the condensed matter and materials physics communities We note that both La and Sr are commonly used dopants in prototypical ferroelectrics such as PLZT ((Pb1−xLax)(Zr1−yTiy)O3), SBT (SrBi2(Ta2O9)), www.nature.com/scientificreports/. The corresponding band gap value is slightly lower than the experimental band gap[53,54,55,56,57], this difference should not significantly affect the trend in electronic and magnetic properties for doped BFO systems

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Conclusion