Perovskite Manganite Trilayers Strain Analysis

Doped manganese oxides with the colossal magnetoresistane (CMR) is a semi-metallic nature of strongly correlated electron system, because of the technical applications in magnetic storage and sensor, people pay more attention to the magnetic oxide material and the magnetic film has been a hot research topic all the time.Because of the coupling effect between layers, based on the quality of technologic application, people were concerned about the low-field magnetoresistance properties, the temperature range and also focused on the magnetic problems in manganese oxide trilayers, such as the interlayer coupling, exchange bias and new-type of magnetic structure between the interfaces and so on. The micro-structure, magnetic anisotropy, magnetic domain changes and the size of magnetoresistance are all directly related to the strain. Therefore, analyzing the strain of the trilayers is helpful to find new way to enhance the low-field magnetoresistance and to make the information functional materials of manganese oxide more practical.In this paper, La0.8Ca0.2MnO3(690A)/La0.5Ca0.5MnO3(x A)/La0.8Ca0.2MnO3(690A) and Pr0.7Sr0.3MnO3(360A)/La0.5Ca0.5MnO3(x A)/Pr0.7Sr0.3MnO3(360A) with different thickness intermediate layer, epitaxially grown on (001)-oriented LaAlO3 and MgO substrate by the pulsed laser deposition (PLD) and the strain of in-plane and out-of-plane of trilayers were analyzed through high-resolution X-ray diffraction. The results showed that La0.8Ca0.2MnO3 layer of the La0.8Ca0.2MnO3/La0.5Ca0.5MnO3/La0.8Ca0.2MnO3 trilayers were in compressive strain state in the horizontal direction, showed e''<0.The interlayer coupling between La0.8Ca0.2MnO3 layer and La0.5Ca0.5MnO3 layer will lead to the further increase of compressive strain with the intermediate layer thickness increases, when the middle layer thickness is 300A, the maximum compressive strain arises, until the intermediate layer thickness of 360A, due to some strain relaxation, in-plane compressive strain begin to reduce.The Pr0.7Sr0.3MnO3 layer of Pr0.7Sr0.3MnO3/La0.5Ca0.5MnO3/Pr0.7Sr0.3MnO3 trilayers is subject to tensile stress in the horizontal direction when the thickness is less than 120 A, showed e''>0; when the thickness is greater than 180A the compressive strain arise due to strain relaxation, leading to e''<0. When La0.5Ca0.5MnO3 middle layer thickness of the trilayers is 60A,120A, very interesting satellite peaks appear in the conventionalθ/2θscan diagram. This is because the interlayer coupling between the ultra-thin La0.5Ca0.5MnO3 layer and Pr0.7Sr0.3MnO3 layer induce shear strain and part of relaxation induced by distortion of Pro.7Sro.3Mn03 layer, leading to the formation of domain structure.