Zn_1−xM_xO (M=Co, Ni, Mn) films with different concentrations of transition metal (10–30%) were synthesized by pulsed laser deposition. The substrates were heated at 400°C and the depositions were performed either under secondary vacuum or under an oxygen pressure of 30 Pa. The occurrence of ion channeling in the films during Rutherford Backscattering Analysis, togetherwith X-ray diffraction, optical absorption and transmission electron microscopy, clearly showthat theMatoms are in solid solution on Zn sites.Magnetic propertieswere investigated by means of magnetometry at 5 and 300 K and Electron Spin Resonance. The Zn_{1 −x}Co_xO and Zn_1−xNi_xO films deposited under low O₂ pressure exhibit both a ferromagnetic and a paramagnetic response up to 300 K, while films deposited under high O₂ pressure and Zn_1−xMn_xO films are paramagnetic. Broad spin resonance peaks are recorded at room temperature, from ferromagnetic films only. The nearly isotropic magnetic response of these films, which is observed in ESR when varying the field orientation with respect to the surface, seems to indicate
that the crystalline anisotropy oppose the shape anisotropy, because of the strong [001] texture of the films.