应变作用下量子顺电材料EuTiO_3的磁电性质

Magnetoelectric properties of quantum paraelectric EuTiO_3 materials on the strain effect

由于磁性和介电性质的强烈耦合,量子顺电材料EuTiO_3材料的研究近来倍受人们的关注.本文通过运用基于密度泛函理论的第一性原理计算研究了量子顺电(PE)材料EuTiO_3的磁性和电子结构,分析了应变对磁性和结构相变的作用,从而探讨了该材料中可能的磁电耦合机理.结果发现,在无应变状态下,EuTiO_3处于顺电立方-G型反铁磁性态,而对于c轴方向的无论张应变还是压应变,当应变增加到一定程度时,由于Ti 3d空轨道与周围O2p电子的杂化平衡被打破,EuTiO_3将相变到铁电(FE)四方-铁磁结构,显示了强烈的自旋一晶格耦合效应.

Because of the strong coupling between the magnetic and dielectric properties, the study of quantum paraelectric EuTiOa has attracted more and more attention in both theoretical and experimental research recently. In this paper, the first principles based on the density functional theory within the generalized gradient approxiamtion is used to investigate the magnetic and electronic structure of quantum paraelectric EuTiO3, and to analyze the effects of the strain on the magnetic and strutural phase transition, in turn to discuss the possible magnetoelectric coupling mechanism of this material. The calculations show that EuTiO3 with the strain-free is in a paraelectric cubic and G-type antiferromagnetic state at low temperature, while appling either compressive or tensile strain along the c-axis to it, the balance of hybridization between Ti 3d and O 2p orbit will be breaken and EuTiO3 will transite from paraelectric and G-antiferromagnetic to ferroelectric-ferromagnetic structure as the strain is increased to a certain value. All those indicate the strong spin-lattice coupling effect in EuTiO3.