应力作用下GdTiO3磁序相变的第一性原理研究
Magnetic phase transition of GdTiO3 under epitaxial strain: A frist-principles study

采用基于密度泛函理论的第一性原理方法, 系统研究了GdTiO3薄膜在压缩应力和拉伸应力作用下的磁序相变. 计算结果表明: 1) 在LaAlO3压缩衬底的作用下, GdTiO3薄膜从铁磁基态转变为G型反铁磁基态. 该结果不同于YTiO3 和LaTiO3在LaAlO3压缩衬底作用时都呈现A型反铁磁基态的情况. 若进一步加大压缩应力, 例如在(001)平面施加YTiO3衬底, 此时GdTiO3薄膜基态才为A型反铁磁态. 2) 在LaScO3和BaZrO3拉伸衬底的作用下, GdTiO3薄膜的基态仍是铁磁态, 但是随着拉伸应力的增大, A型反铁磁态的能量和铁磁态的能量差逐渐缩小, 即GdTiO3薄膜的基态有转变为A型反铁磁态的趋势. 3) 在外加应力的作用下, GdTiO3薄膜基态的磁序发生了相变, 但是其绝缘性并没有变, 说明GdTiO3薄膜仍为Mott型绝缘体.
The magnetic phase transition of GdTiO3 films under the compressive strain and tensile strain have been studied by the first-principles method based on the density functional theory. The calculations show that: 1) The ground state of GdTiO3 film on the LaAlO3 substrate changes from the original ferromagnetism to G-type antiferromagnetism, different from the YTiO3 and LaTiO3 cases both of which becomes the A-type antiferromagnetism on the (001) LaAlO3 substrate. If the in-plane compressive strain is large enough, e.g. on the (001) YAlO3 substrate, the ground state finally becomes the A-type one. 2) For the tensile strain, the LaScO3 and BaZrO3 substrates have been tested, the ground state of GdTiO3 films are also ferromagnetism, but the energy difference between A-type antiferromagnetism and ferromagnetism decreases with increasing the tensile strain, which show a tendency to transit to the A-type one. 3) The GdTiO3 films remain insulating under strain with magnetic phase transition, which show these films are also Mott-insulators.