Magnetic Properties and Spontaneous Polarization of La-, Mn- and N-Doped Tetragonal BiFeO3: A First-Principles Study

Qiuhong Tan,Qianjin Wang,Yingkai Liu

doi:10.3390/ma11060985

Abstract

Multiferroic materials have been receiving attention for their potential applications in multifunctional devices. Chemical substitution is an effective method for improving the physical properties of BiFeO3 (BFO). However, different experimental results have been reported for Lanthanum- (La-) and Manganese (Mn) -doped BFO ceramics. Here, we systematically studied the magnetic properties and spontaneous polarization of La-, Mn-, and Nitrogen (N) -doped tetragonal BiFeO3 using density functional theory with the generalized gradient approximation and U-value method. The calculated results demonstrated that the systems show ferromagnetism with Mn and N doping, whereas no magnetization was found with La doping in G- and C-type antiferromagnetic orderings. Our research further revealed that the ferromagnetism is attributed to the p-d orbital hybridization. Berry-phase polarization calculations predicted a large polarization of 149.2 µC/cm2 along the [001] direction of pure tetragonal BFO. We found that La and N substitution had little influence on the spontaneous polarization, whereas Mn substitution reduced the spontaneous polarization. The reduced energy barrier heights of the doped systems indicate the reduced stability of the off-centering ferroelectricity against the thermal agitation. These findings provide greater understanding for controlling and tuning the multiferroic properties of BFO.

Highlights

Multiferroic materials are receiving considerable attention for their potential applications in multifunctional devices [1,2]
Chemical substitution is an effective method to improve the performance of BFO and many experimental studies have been reported on the A- and B-site substitution of BFO [3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24]
Different experimental results were reported in La- and Mn-doped BFO thin films

Summary

Introduction

Multiferroic materials are receiving considerable attention for their potential applications in multifunctional devices [1,2]. Some experimental investigations reported that La-doped BFO films enhanced ferroelectric remnant polarization and improved ferromagnetic properties [8,17,18,19]. Materials 2018, 11, 985 reported that La-doped BFO film showed weak ferromagnetism. High-strain BFO thin film has a tetragonal structure, which was reported in many experimental and theoretical studies [26,27,28,29,30]. In this work, the multiferroic properties of La and Mn substitution at the A-site and B-site of tetragonal BFO were investigated by using first-principles. Substitution at the O-site of tetragonal BFO was investigated as a new method of improving the multiferroic properties of BFO because room temperature ferromagnetism was reported in N-doped. Our work highlights the explicit physical mechanism of the multiferroic properties of La-, Mn-, and N-doped BFO films and provides useful guidance for improving the multiferroic properties of BFO

Computational Details

Results and Discussion

Conclusions