应力效应对La_(0.8)Ba_(0.2)MnO_3薄膜电磁学特性的影响

Strain-induced modulation of electrical and magnetic properties in La_(0.8)Ba_(0.2)MnO_3 thin films

以相同的生长条件,在(LaAlO_3)_(0.3)(Sr_2AlTaO_6)_(0.7)(LSAT)衬底上制备不同厚度的La_(0.8)Ba_(0.2)MnO_3(LBMO)薄膜。由于薄膜厚度与薄膜应变之间的正相关关系,LBMO薄膜的厚度一定程度上决定了其磁学特性。LBMO薄膜与LSAT衬底的晶格失配导致LBMO在面内受到压应力,在垂直面内受到拉应力,拉应力趋向于使面内晶格常数增大,而压应力起到相反的作用,会使纵向晶格常数变小。因此,随着薄膜厚度的减小,压应力增加,从而引起薄膜的纵向晶格常数变小。LBMO的晶格畸变必然导致其能带结构的变化,从而在宏观上诱发磁电阻效应的改变。

Under the same deposition conditions,La（0.8）Ba（0.2）MnO3（LBMO） thin films with different thickness were grown on the（LaAlO3）（0.3）（Sr2AlTaO6）（0.7）（LSAT） substrates. Due to the proportional relationship between thickness and strain of LBMO films, the thickness of LBMO thin film determines their magnetic properties. The lattice mis-matching between LBMO film and LSAT substrate causes the in-plane compressive strain accompanied by the out-of-plane tensile strain. In-plane compressive strain tends to decrease the lattice constants along a-axis and b-axis, while out-of-plane tensile strain may increase the lattice constants along c-axis. Therefore, with the films thinning the increasing strain effect induces the distortion of the films＇ lattice structure. This may change the band structure inevitably, thereby inducing the modulation of electrical and magnetic properties in LBMO films.