In this thesis, the effect of intrinsic and exrtinsic stress on manganese oxides (manganites) has been investigated. The crystalline structure of these compounds is octahedral, and the strain is created by the changes in the octahedral. Many factors can lead to stre however, the atoms with different ionic radii will create intrinsic stress and the lattice mismatch between film and substrate creates an exrtinsic stress. Accordingly, the effect of intrinsic and exrtinsic stress on three structures, i.e., La 0.8 - x A x Sr 0.2 MnO 3 (LASMO) with a strong ferromagnetic phase, La 0.4 Pr 0.3 Ca 0.3 MnO 3 (LPCMO) structure with the coexistence of ferromagnetic and antiferromagnetic phases, and La 0.5 Ca 0.5 MnO 3 (LCMO) with strong charge order was investigated, and the results are reported in three separate sections. In the first section, the effect of the inherent stress caused by the doping of atoms (Ce, Pr, Nd, Gd) at the lanthanum position in the LSMO structure was investigated. The samples indicate the single-phase formation to Pr and Nd doping, but it reveals a secondary phase in Ce and Gd doping. By increasing concentration in Pr and Nd doping, Curie temperature shifts to lower temperature, while the Gd and Ce doping Curie temperature does not behavior regularly. Spin glass phenomena occurs in Pr and Nd doping, but there is no spin glass in Gd and Ce doping. However, the electrical behavior of the samples is in good agreement with the magnetic behavior. Increasing the Pr doping reduces the entropy changes and the amount of RCP. The samples with 2‰ fixed doping have a second order phase transition for Pr, Nd, and Ce atoms. The obtained values of entropy changes of the samples under an applied magnetic field of 25 kOe are 3.50, 2.64 and 3.34J kg -1 K -1 for Ce, Pr and Nd doped samples, respectively. The RCP values of LSMO, Nd and Pr doped samples at 2.5T are 112.84, 121.24 and 136.22Jkg -1 , respectively. In the second part, the effect of inherent stress caused by the replacement of Pb and Al elements in the position of Ca and Mn in LCMO, respectively, and the exrtinsic stress created by a change in the thickness of the LCMO films on the LAO and STO substrates were investigated. With the increase of Al concentration in the LCMO structure, the phase coexistence decreases. Moreover, magnetization curves in FC and ZFC modes are different fit in doping less than 0.1, while they coincide with higher doping. Such behavior is also observed in measuring electrical resistivity of samples. The Pb substitution with a larger ion radius compared with Ca in the LCMO structure increases the ferromagnetic phase and Curie temperature. The entropy changes enhanced with the increase of Pb to 0.1 doping and then decreased in 0.2 doping. The RCP value for the pure sample represents the highest value and has the lowest value at x=0.1. In the following, the exrtinsic stress caused by the change in thickness and the substrate effects in the LCMO structure was investigated. In the STO films, decreasing the thickness of the CE strengthened the antiferromagnetic phase. Therefore, in this phase the saturation magnetization decreases and in the magnetic field of 9 Tesla, phase transition is not observed. For LAO films, there exists the CE antiferromagnetic phase in high thicknesses, while decreasing thicknesses leads to the emergence of a C-type AFM state. At high thickness, transition temperature was observed for the fields above 4T, while transition temperature decreased by increasing magnetic fields. In the third section, the effect of pulse repetition rate, thickness and stress on the thin films of the LPCMO structure was investigated. At pulse repetition rate of 2, 5, and 7 Hz, the strain was equal, while it increased at 10 Hz. The Curie temperature is consistent with the temperature of the metal insulator transition in the different repetition rate and thicknesses. Measurements of magnetization in both ZFC and FCC states indicate that there is a dead layer in the 10-Hz sample; therefore, the resistance increase and saturation magnetization decreace for this sample. Also, in the lower thickness, the dead layer forms in between the film and substrate interfaces. Finally, the effect of tensile stress caused by the NGO substrate was studied by changing the layering conditions (changing the substrate distance from the target) as well as the annealing of the layers. When the substrate's distance from the target is high, the layers grow epitaxially, while with reducing the distance, there is a polycrystalline growth in addition to the growth along the substrate. The measurement of AMR was performed in fields less than one Tesla, which revealed the highest value for non-annealed samples in the range of 0.5-0.7 Tesla.