Abstract: The dissertation addresses how the interaction between two magnetic layers changes the magnetic properties. The dissertation is divided into three sections, chapters 1,2 and 3 introduce the magnetic films, basic theories and experimental methods. Second part, Chapters 4,5 and 6 describe the projects related with magnetic phase transitions and the effect of coupling on them. The third part, Chapters 7,8 and 9 describe the projects related with magnetization direction; spin reorientation transition in Ni/Cu(001), the effect of interlayer coupling on the magnetization direction, and the exchange bias effect in the coupled ferromagnetic system. In the magnetic phase transition projects, the effect of anisotropy and long-range dipole interaction on the Curie temperature is studied in the Fe/Ni/Cu(001)system first. Curie temperature is measured around stripe domain forming spin reorientation transition regions, in which it is found the anisotropy and the long range dipole interaction is important to build magnetic order. Secondly, the effect of indirect exchange coupling on the Curie temperature is studied; there are three kinds of phase transitions. When one film is in the ferromagnetic state, the coupling increases the Curie temperature of the other film. Both films can have simultaneous phase transitions when the Curie temperatures are similar. Thirdly, the Neel temperature and Curie temperature are discussed when the antiferromagnetic layer and ferromagnetic layers are coupled. The randomly uncompensated magnetic moments induced by antiferromagnetic material decrease the Curie temperature of the ferromagnetic film. In the magnetization direction studies, first, the spin reorientation behaviors of the Ni/Cu(001) system is discussed. The evidence of oscillatory behavior of the anisotropy of the system is found. Secondly, the effect of coupling on the magnetization direction is discussed in the Ni/Fe/Co/Cu(001) system. It is found that only collinear part of magnetization is coupled in the region of a slowly rotating spin reorientation transition. Lastly, the exchange bias in the coupled ferromagnetic system is studied.