应力作用下GdTiO_3磁序相变的第一性原理研究

采用基于密度泛函理论的第一性原理方法,系统研究了GdTiO_3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LaAlO_3压缩衬底的作用下,GdTiO_3薄膜从铁磁基态转变为G型反铁磁基态.该结果不同于YTiO_3和LaTiO_3在LaAlO_3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YTiO_3衬底,此时GdTiO_3薄膜基态才为A型反铁磁态.2)在LaScO_3和BaZrO_3拉伸衬底的作用下,GdTiO_3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GdTiO_3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,GdTiO_3薄膜基态的磁序发生了相变,但是其绝缘性并没有变,说明GdTiO_3薄膜仍为Mott型绝缘体.

Magnetic phase transition of GdTiO3 under epitaxial strain: A frist-principles study

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.