The strain effect on La0.67Ca0.33MnO3 and La0.8Ba0.2MnO3 thin films on SrTiO3 (001) substrate with different thicknesses has been studied by X-ray absorption near edge spectroscopy (XANES), which can reveal the details of the coupling between cations and anions. The strain may suppress the TC of LCMO films while enhancing that of LBMO films. The theoretical calculation results suggest the unoccupied states of the third structure of XANES are formed by much more complex hybridization of O 2p to Mn 4sp, La 6s and (Ca 4sp or Ba 6sp) orbitals. The change of the absorption intensity of the second and third structures is compatible to the TC change of both films due to the strain effect. This strongly suggests that the strain effect on LCMO and LBMO thin films is mainly associated with the bonding situation between O and La(Ca or Ba) ions.

Abstract It is know that the crystal structure and the magnetic ordering in La1-xAxMnO3(A=Ca,Sr,Ba) may disrupted by introducing various defect. This disorder weakens the Hund coupling and, thus, the double-exchange interaction between Mn3+ and Mn4+. Combining with John-Teller distortion enhanced by the defects, the magnetoresistance (MR) effect is enhanced. Up to date, the generated defects were mostly columnar defects or chemical substitution defects. In this study we generated different type of defect, point defects, and inrestigate its effect on MR effect. La0.7Sr0.3MnO3 and La0.7A0.3MnO3 films were deposit on LaAiO3 (001) and SrTiO3 (001) substrates by pulse laser deposition technique. Films were patterned with a standard photolithography. Point defects were introduced by irradiated high (1.7 and 3MeV) and low (10KeV) energy protons. We found that, the low dose sample exhibits both conductivity and the low field MR enhancement. Which were believed due to introduce acceptor level and the magnetic structure defects. When the dose was high, the structure defects leaded strong scattering effect that lowed the conductivity. The MR in high dose sample was also enhanced near by transition temperature.