Growth and structural, magnetic, and magnetooptical properties of ZnO films doped with a Fe$^{57}$ 3$d$ impurity

ZnO films obtained by high-frequency magnetron sputtering and doped with a Fe$^{57}$ metallic 3$d$ impurity by the diffusion method are studied. The type of local environment of Fe$^{57}$ impurity atoms on varying the deposition parameters of ZnO films is determined by Mössbauer spectroscopy. It is established that the ground state of Fe$^{57}$ impurity atoms corresponds to metallic iron in the magnetically ordered state and there is a small fraction of Fe$^{57}$ atoms with a local environment corresponding to the complex oxide Fe$_3$O$_4$, having the magnetically ordered state; there is also a fraction of iron atoms in the paramagnetic state. The magnetic and magnetooptical parameters of the films were measured using magnetooptic Kerr effect. The spectral dependences of the polar magnetooptic Kerr effect in ZnO(Fe$^{57}$) films are measured in a photon energy range of 1.5–4.5 eV and simulated by the effective-medium method. It is established that ZnO(Fe$^{57}$) possess an easy-plane magnetic anisotropy with a magnetization lying in the film plane.