Thickness Dependence on the Magnetism in Mo-Capped Epitaxial Fe Films

When magnetic metal films are oxidized, in many cases, their saturation magnetization values decrease. The importance of high magnetization is well-known because it is directly related to the maximum energy product. Thus, prevention of oxidation in magnetic metal films via capping is important not only for studying the magnetism in magnetic metal films but also for developing new packaging technology for such films. In this research, we successfully grow epitaxial (110) Fe films on (0001) Al2O3 substrates by using radio-frequency (RF) magnetron sputtering. We capped 10-nm-thick Mo layers on the Fe films to prevent oxidation. By varying the thickness of the films, we systematically observed the changes in both the coercivity and the saturation magnetization. Especially, when the film’s thickness was below 8.5 nm, the coercivity of the film started to decrease. We believe the drastic change in the coercivity appeared in the Fe films when the film’s thickness approached the critical domain size for a magnetic domain transition.